++ Prevention ++

This page will be updated on 28 February. In the meantime, check new papers at https://covidreference.com/top10.


12 February

Brooks JT, Beezhold DH, Noti JD, et al. Maximizing Fit for Cloth and Medical Procedure Masks to Improve Performance and Reduce SARS-CoV-2 Transmission and Exposure, 2021. MMWR Morb Mortal Wkly Rep. ePub: 10 February 2021. DOI: http://dx.doi.org/10.15585/mmwr.mm7007e1

From half-mask to double mask – the US is trying to make up ground on the disastrous first-year management of the COVID-19 pandemic. The CDC (finally, back!) conducted experiments to assess two ways of improving the fit of medical procedure masks: fitting a cloth mask over a medical procedure mask (double masking), and knotting the ear loops of a medical procedure mask and then tucking in and flattening the extra material close to the face. Each modification substantially improved source control and reduced wearer exposure. See also Glenza J. CDC study recommends double masking to reduce Covid-19 exposure. The Guardian 2021, published 10 February. Full-text: https://www.theguardian.com/world/2021/feb/10/mask-guidance-cdc-two-masks-close-fitting.


11 February

Reddy S. Double Face Masks? N95? Protect Yourself Against New Covid-19 Variants With These Mask Upgrades. WSJ 2021, published 4 February. Full-text: https://www.wsj.com/articles/double-face-masks-n95-protect-yourself-against-new-covid-19-variants-with-these-mask-upgrades-11612473349

As new, more-contagious coronavirus variants circulate, doctors say it’s important to improve the effectiveness of your mask practices—such as by “double masking”, to wear two at once. Numerous studies have found that masks help protect the wearers as well as those around them from the virus that causes COVID-19.


Tan IB, Tan C, Hsu LY, et al. Prevalence and Outcomes of SARS-CoV-2 Infection Among Migrant Workers in Singapore. JAMA. 2021 Feb 9;325(6):584-585. PubMed: https://pubmed.gov/33560312. Full-text: https://doi.org/10.1001/jama.2020.24071

Singapore 2020: 200.000 migrant workers exposed to SARS-CoV-2, 111.000 confirmed infections, 20 ICU patients, 1 death. How did they acheive that? Mass testing and isolation.


4 February

Krammer F. Pandemic Vaccines: How Are We Going to Be Better Prepared Next Time? Med (N Y). 2020 Dec 18;1(1):28-32. PubMed: https://pubmed.gov/33521752. Full-text: https://doi.org/10.1016/j.medj.2020.11.004

We did good, but in the future, we can do better. Discover Florian Krammer’s 3-month timeline for developing vaccines against the next pandemic.


31 January

Mack CD, Wasserman EB, Perrine CG, et al. Implementation and Evolution of Mitigation Measures, Testing, and Contact Tracing in the National Football League, August 9–November 21, 2020. MMWR Morb Mortal Wkly Rep 2021;70:130–135. DOI: http://dx.doi.org/10.15585/mmwr.mm7004e2

Prevention works. This CDC paper is broadly applicable throughout society to limit the spread of the virus, including in settings such as long-term care facilities, schools, and high-density environments.


Lewis D. COVID-19 rarely spreads through surfaces. So why are we still deep cleaning? Nature 2021, published 29 January. Full-text: https://www.nature.com/articles/d41586-021-00251-4

The coronavirus behind the pandemic can linger on doorknobs and other surfaces, but these aren’t a major source of infection.


21 January

Goyal R, Hotchkiss J, Schooley RT, et al. Evaluation of SARS-CoV-2 transmission mitigation strategies on a university campus using an agent-based network model. Clinical Infectious Diseases January 19, 2021. Full-text: https://doi.org/10.1093/cid/ciab037

Continue wearing your mask! Interesting modeling study, investigating the impact of risk mitigation interventions at the University of San Diego. The authors assessed four scenarios with varying housing, instructional, and behavioral characteristics. The main message: structural interventions for housing (singles only) and instructional changes (from in-person to hybrid with class size caps) can substantially reduce R0, but masking and social distancing are required to reduce this to 1 or below.


Rader B, White LF, Burns MR, et al. Mask-wearing and control of SARS-CoV-2 transmission in the USA: a cross-sectional study. The Lancet Digital Health January 19, 2021. Full-text: https://doi.org/10.1016/S2589-7500(20)30293-4

Again, masks work. This large web platform randomly surveyed almost 400.000 US individuals aged 13 years and older, to ask about face mask wearing. A logistic model controlling for physical distancing, population demographics and other variables found that a 10% increase in self-reported mask wearing was associated with an increased odds of transmission control (odds ratio 3,53, 95% CI 2,03–6,43). Communities with high reported mask wearing and physical distancing had the highest predicted probability of transmission control.


17 January

Barnett BS, Carlo AD, Mezzadri A, Ruwanpura KN. The Invisible People Behind Our Masks. Ann Intern Med. 2021 Jan 12. PubMed: https://pubmed.gov/33428438. Full-text: https://doi.org/10.7326/M20-7421

In our unprecedented efforts to rapidly secure large quantities of PPE, regulators have been inconsistent in addressing the unsettling truths about where some of it may originate. To contain the human cost of the pandemic, there is no doubt that we should maximize effective use of PPE, but Brian Barnett et al. argue that we must also ensure better work practices for those who enable us to wear it in the first place.


14 January

Fuller JA, Hakim A, Victory KR, et al. Mitigation Policies and COVID-19–Associated Mortality — 37 European Countries, January 23–June 30, 2020. MMWR Morb Mortal Wkly Rep. ePub: 12 January 2021. DOI: http://dx.doi.org/10.15585/mmwr.mm7002e4

European countries that implemented more stringent mitigation policies by the time they reached an early mortality threshold in spring 2020 (closure of non-essential businesses, restrictions on gatherings and movement, and stay-at-home orders) tended to report fewer COVID-19–associated deaths through the end of June. These countries have saved tens of thousands of lives relative to those countries that implemented similar policies, but later. These findings suggest that earlier implementation, even by just a few weeks (even one week!), may prevent widespread transmission and large numbers of deaths.


13 January

Atherstone C, Peterson ML, Malone M, et al. Time from Start of Quarantine to SARS-CoV-2 Positive Test Among Quarantined College and University Athletes — 17 States, June–October 2020. MMWR Morb Mortal Wkly Rep 2021;70:7–11. DOI: http://dx.doi.org/10.15585/mmwr.mm7001a2

Quarantine after SARS-CoV-2 exposure is critical to preventing transmission. Among young, healthy athletes, the probability of receiving positive test results after day 10 of quarantine is low. A shorter quarantine after COVID-19 exposure could increase adherence but still pose a small residual risk for transmission.


Jones A, Fialkowski V, Prinzing L, Trites J, Kelso P, Levine M. Assessment of Day-7 Postexposure Testing of Asymptomatic Contacts of COVID-19 Patients to Evaluate Early Release from Quarantine — Vermont, May–November 2020. MMWR Morb Mortal Wkly Rep 2021;70:12–13. DOI: http://dx.doi.org/10.15585/mmwr.mm7001a3

Among the persons in quarantine who tested negative at day 7 after exposure, none who were retested between days 8 and 14 were positive. Allowing asymptomatic persons to shorten quarantine with a negative test at day 7 or later has not been demonstrated to result in transmission of SARS-CoV-2.


12 January

Meidan D, Schulmann N, Cohen R, et al. Alternating quarantine for sustainable epidemic mitigation. Nat Commun 12, 220 (2021). Full-text: https://doi.org/10.1038/s41467-020-20324-8

To ease the potentially devastating socioeconomic consequences of pharmaceutical interventions, social distancing, lock-downs and mobility restrictions, Baruch Barzel, Dror Meidan and colleagues, propose an alternative alternaitng quarantine strategy: at any moment, half of the population remains under lockdown while the other half continues to be active – maintaining a routine of weekly alternation of activity and quarantine. This regime would minimize infectious interactions, as it allows only half of the population to interact for just half of the time. Dramatic reduction in transmission despite sustaining socioeconomic continuity at ~50% capacity?


10 January

Brainard J, Jones NR, Lake IR, Hooper L, Hunter PR. Community use of face masks and similar barriers to prevent respiratory illness such as COVID-19: a rapid scoping review. Euro Surveill. 2020 Dec;25(49):2000725. PubMed: https://pubmed.gov/33303066. Full-text: https://doi.org/10.2807/1560-7917.ES.2020.25.49.2000725

Does wearing face masks reduce primary respiratory infection risk by only 6–15%? See also the comment by Cowling BJ, Leung GM. Face masks and COVID-19: don’t let perfect be the enemy of good. Euro Surveill. 2020 Dec;25(49):2001998. PubMed: https://pubmed.gov/33303063. Full-text: https://doi.org/10.2807/1560-7917.ES.2020.25.49.2001998


9 January

Davidson BL, Tapson VF, Irwin RS, French CL, Elliott CG, Levi M. Commentary: Pharyngeal Antisepsis to Reduce COVID-19 Pneumonia. Am J Med. 2020 Dec 15:S0002-9343(20)31114-1. PubMed: https://pubmed.gov/33338507. Full-text: https://doi.org/10.1016/j.amjmed.2020.12.001

Might “washing your throat” with a pharyngeal antisepsis before sleeping, when healthy adults of all ages aspirate material from above the larynx, help protect individuals against COVID-19 pneumonia? Find out why Bruce Davidson et al think it may.


4 January

Storm N, McKay LGA, Downs SN, et al. Rapid and complete inactivation of SARS-CoV-2 by ultraviolet-C irradiation. Sci Rep. 2020 Dec 30;10(1):22421. PubMed: https://pubmed.gov/33380727. Full-text: https://doi.org/10.1038/s41598-020-79600-8

SARS-CoV-2 is able to survive on surfaces for extended periods of time. Although contact with surfaces contaminated with droplets generated by infected persons through exhaling, talking, coughing and sneezing is not the major driver of SARS-CoV-2 transmission (the main driver is speaking to and coughing, shouting and sneezing at people), it would be useful to inactivate SARS-CoV-2 on contaminated surfaces. Here, Anthony Griffiths, Nadia Storm and colleagues describe the almost instantaneous inactivation of SARS-CoV-2 in both wet and dry format using radiation generated by a commercially available ultraviolet (UV)-C light source at 254 nm.


3 January

Rolfes MA, Grijalva CG, Zhu Y, et al. Implications of Shortened Quarantine Among Household Contacts of Index Patients with Confirmed SARS-CoV-2 Infection – Tennessee and Wisconsin, April-September 2020. MMWR Morb Mortal Wkly Rep. 2021 Jan 1;69(5152):1633-1637. PubMed: https://pubmed.gov/33382676. Full-text: https://doi.org/10.15585/mmwr.mm695152a1

One of your household members is diagnosed with SARS-CoV-2 infection. Is a 7-day quarantine enough (7 days after the symptom onset of the index patient) even if you are asymptomatic and have a negative laboratory test result? Not always, because 19% of people in your situation will experience symptoms or receive positive test results in the following week. The recommendation by Melissa Rolfes, et al.: persons released from quarantine before 14 days should continue to avoid close contact and wear masks when around others until 14 days after their last exposure.


Okyere I, Chuku EO, Ekumah B, et al. Physical distancing and risk of COVID-19 in small-scale fisheries: a remote sensing assessment in coastal Ghana. Sci Rep. 2020 Dec 29;10(1):22407. PubMed: https://pubmed.gov/33376254. Full-text: https://doi.org/10.1038/s41598-020-79898-4

Fish landing sites along the Ghana coast could be transmission hotspots. To get a clearer picture, Isaac Okyere et al. employed an unmanned aerial vehicle. Aerial measurements taken at times of peak landing beach activity indicated that the highest proportion of people, representing 56%, 48%, 39% and 78% in Elmina, Winneba, Apam and Mumford respectively, were located at distances of less than one meter from their nearest neighbor.


2 January

Madas BG, Füri P, Farkas Á, et al. Deposition distribution of the new coronavirus (SARS-CoV-2) in the human airways upon exposure to cough-generated droplets and aerosol particles. Sci Rep 2020, published 31 December. Full-text: https://doi.org/10.1038/s41598-020-79985-6

Severe, potentially fatal pneumonia supposes that SARS-CoV-2 reaches the acinar airways. What if we reduced the number of viruses getting there? After characterizing the deposition distribution of SARS-CoV-2 in the airways upon exposure to cough-generated droplets and aerosol particles, Balázs Madas et al. found that the number of viruses deposited in the extra-thoracic airways is about 7 times higher than in the acinar airways. The authors hypothesize that most cases of COVID-19 pneumonia might be preceded by SARS-CoV-2 infection of the upper airways and that without the enhancement of viral load in the upper airways, COVID-19 would be much less dangerous. Ergo, we should use the period between the onset of initial symptoms and the potential clinical deterioration to block or significantly reduce the transport of virus towards the acinar airways, for example with non-specific treatment forms like disinfection of the throat and nasal and oral mucosa. In any case, recommend the authors, use a tissue or cloth in order to absorb droplets and aerosol particles emitted by your own coughs and sneezes… before re-inhalation! Even if you are alone in quarantine.


31 December

Chiba H, Lewis M, Benjamin ER, et al. “Safer at Home”: The effect of the Covid-19 Lockdown on Epidemiology, Resource Utilization and Outcomes at a Large Urban Trauma Center. J Trauma Acute Care Surg. 2020 Dec 17. PubMed: https://pubmed.gov/33347094. Full-text: https://doi.org/10.1097/TA.0000000000003061

Spring 2020 lockdown in California. At the largest trauma center in Los Angeles, there was a reduction in the automobile versus pedestrian admissions by 42,5%, motorcycle injuries by 38,7%, and bicycle accidents by 28,4%, but no significant effect on the number of motor vehicle accident admissions. There was an increase in ground level falls by 32,5%, especially in the elderly group. The absolute number of gunshot wounds increased by 6,2% and knife injuries by 39,3%. Suicides increased by 38,5%. L


29 December

Tinson A, Clair A. Better housing is crucial for our health and the COVID-19 recovery. The Health Foundation 2020, published 28 December. Full-text: https://www.health.org.uk/publications/long-reads/better-housing-is-crucial-for-our-health-and-the-covid-19-recovery

In this Long read, Adam Tinson and Amy Clair summarize why housing problems are likely to be a significant component of the SARS-CoV-2 pandemic that has led to greater risks of COVID-19 infection and serious complications for certain social groups. The authors conclude that overcrowding, poor quality and unaffordable homes are a threat to health.


28 December

Baggett TP, Scott JA, Le MH, et al. Clinical Outcomes, Costs, and Cost-effectiveness of Strategies for Adults Experiencing Sheltered Homelessness During the COVID-19 Pandemic. JAMA Netw Open. 2020;3(12):e2028195. Full-text: https://doi.org/10.1001/jamanetworkopen.2020.28195

A modeling study of simulated adults living in homeless shelters. Daily symptom screening with PCR testing of individuals who had positive symptom screening paired with non-hospital care site management of people with mild to moderate coronavirus disease 2019 (COVID-19) was associated with a substantial decrease in infections and lowered costs.


27 December

Martin CA, Jenkins DR, Patel P, et al. No cases of asymptomatic SARS-CoV-2 infection among healthcare staff in a city under lockdown restrictions: lessons to inform ‘Operation Moonshot’. J Pub Health 2020, published 26 December. Full-text: https://doi.org/10.1093/pubmed/fdaa237

Imagine inviting more than 13.000 healthcare workers (HCWs) to get SARS-CoV-2 testied. Now about 8% (n = 1150) of the workforce volunteer and you find no cases of asymptomatic SARS-CoV-2 infection. You would probably conclude, like Manish Pareek, Christopher Martin and colleagues, that voluntary testing of asymptomatic staff may not be cost-effective.


25 December

Brown M. Flay your fart: viral clip calls on public to alter speech to curb Covid. The Guardian 2020, published 21 December. Full-text: https://www.theguardian.com/culture/2020/dec/21/flay-your-fart-viral-clip-calls-on-public-to-alter-speech-to-curb-covid?utm

A retired PR consultant and translator has produced a video suggesting the government is to ban certain sounds and letters of the alphabet because they increase the transmission of COVID-19. Instead of “please take care”, we should say “flease nake lare”, says the skit.


23 December

Mina MJ, Andersen KG. COVID-19 testing: One size does not fit all. Science 2020, published 21 December. Full-text: https://doi.org/.1126/science.abe9187

A one-sentence abstract by Michael Mina and Kristian Andersen: “To control the pandemic, testing should be considered a public health tool.” Discover the world of SARS-CoV-2 testing one year into the pandemic.


Swaminathan S. The WHO’s chief scientist on a year of loss and learning. Nature 2020, published 17 December. Full-text: https://www.nature.com/articles/d41586-020-03556-y

The head of scientific work at the World Health Organization reflects on the agency’s challenges and achievements as it navigates the COVID pandemic.


22 December

Spaccaferri G, Larrieu S, Pouey J, et al. Early assessment of the impact of mitigation measures to control COVID-19 in 22 French metropolitan areas, October to November 2020. Euro Surveill. 2020;25(50):pii=2001974. https://doi.org/10.2807/1560-7917.ES.2020.25.50.2001974

To control this second SARS-CoV-2 pandemic wave, French national and local authorities implemented a series of mitigation measures in certain metropolitan areas starting mid-October, followed by a countrywide lockdown on 30 October. Here, Guillaume Spaccaferri, Sophie Larrieu and colleagues assess the impact and timeliness of these measures, mainly curfews, describing COVID-19 spread and severity in the 22 French metropolitan areas. A considerable decrease in incidence and hospital admissions was observed 7 to 10 days after the measures were put in place, occurring earlier in metropolitan areas where these had first been undertaken.


Tufekci Z. Hang On for 3 More Months. The Atlantic 2020, published 17 December. Full-text: https://www.theatlantic.com/ideas/archive/2020/12/wait-until-march/617410/

Some simple advice for anyone contemplating a holiday gathering: Wait until March or Easter 2021: 4 April.


21 December

Spaccaferri G, Larrieu S, Pouey J, et al. Early assessment of the impact of mitigation measures to control COVID-19 in 22 French metropolitan areas, October to November 2020. Euro Surveill 2020;25(50):pii=2001974. Full-text: https://doi.org/10.2807/1560-7917.ES.2020.25.50.2001974

In France, measures including curfew and lockdown were implemented to control the COVID-19 pandemic second wave in 2020. This study found a considerable decrease in incidence of COVID-19 cases and hospital admissions 7 to 10 days after mitigation measures were put in place, occurring earlier in metropolitan areas.


20 December

Priesemann V, Brinkmann MM, Ciesek S, et al. Calling for pan-European commitment for rapid and sustained reduction in SARS-CoV-2 infections. Lancet December 18, 2020. Full-text: https://doi.org/10.1016/S0140-6736(20)32625-8

In their comment (which was signed by > 200 researchers), the authors urge governments throughout Europe to agree on clearly formulated common goals, coordinate their efforts, develop regionally adapted strategies to reach the goals, and thereby work resolutely towards lowering case numbers.


18 December

Salathé M, Althaus C, Anderegg N, et al. Early evidence of effectiveness of digital contact tracing for SARS-CoV-2 in Switzerland. Swiss Med Wkly. 2020 Dec 16;150:w20457. PubMed: https://pubmed.gov/33327003. Full-text: https://doi.org/10.4414/smw.2020.20457

COVID apps may work (at least in Switzerland!). By 10 September 2020, the SwissCovid app (it uses the EN framework to estimate proximity between phones) has been downloaded 2,36 million times. Marcel Salathé and colleagues estimate that digital contact tracing can show similar effectiveness at identifying infected partners of index cases as classic contact tracing, provided that both the index case and the exposed contacts use the app. These apps represent a helpful complementary tool for controlling the spread of SARS-CoV-2. Please download your local app.


17 December

Xie Y, Bowe B, Maddukuri G, et al. Comparative evaluation of clinical manifestations and risk of death in patients admitted to hospital with covid-19 and seasonal influenza: cohort study. BMJ 15 December 2020; 371. Full-text: https://doi.org/10.1136/bmj.m4677

Is COVID-19 a flu (no)? Or is it more severe and deadly than seasonal influenza (yes)? Yan Xie and colleagues have compared patients admitted to hospital with COVID-19 between 1 February 2020 and 17 June 2020 (n = 3641) and seasonal influenza between 2017 and 2019 (n = 12.676). COVID-19 was associated with higher risk of acute kidney injury (odds ratio 1.52), incident renal replacement therapy (4.11), severe septic shock (4.04), vasopressor use (3.95), pulmonary embolism (1.50), deep venous thrombosis (1.50), stroke (1.62), acute myocarditis (7.82), arrythmias and sudden cardiac death (1.76). Compared with seasonal influenza, COVID-19 was also associated with higher risk of death (HR 4.97), mechanical ventilator use (4.01), and admission to intensive care (2.41). You may use this data for discussions with COVID-19 deniers (meh, they won’t believe you anyway).


Brauner JM, Mindermann S, Sharma Mm et al. Inferring the effectiveness of government interventions against COVID-19. Science 15 Dec 2020: eabd9338. Full-text: https://science.sciencemag.org/content/early/2020/12/15/science.abd9338

Jan M. Brauner and colleagues from Oxford evaluated the impact of several NPIs on the epidemic’s growth in 34 European and 7 non-European countries by using a Bayesian hierarchical model. Good to know during these days of a second lockdown: closing all educational institutions, limiting gatherings to 10 people or less, and closing face-to-face businesses each reduced transmission considerably. Interestingly, the additional effect of stay-at-home orders was comparatively small.


16 December

McLellan A, Godlee F. Covid 19: Christmas relaxation will overwhelm services. BMJ 2020, published 15 December. Full-text: https://doi.org/10.1136/bmj.m4847

Since the UK’s first lockdown in March, the government has had one (perhaps only one) consistent message—protect the NHS. Now, with the number of hospital patients with COVID-19 again on the rise, and a third wave almost inevitable, the New Year is likely to see NHS trusts facing a stark choice: be overwhelmed or stop most elective and non-urgent work. Rather than lifting restrictions over Christmas as currently planned, the UK should follow the more cautious examples of Germany, Italy, and the Netherlands. To protect the NHS, the UK government must abandon plans for household mixing.


Lewis D. Why many countries failed at COVID contact-tracing — but some got it right. Nature 2020, published 14 December. Full-text: https://www.nature.com/articles/d41586-020-03518-4

Nine months after the World Health Organization (WHO) declared COVID-19 a pandemic, few countries are wielding contact-tracing effectively. Even rich nations have struggled with one of the most basic and important methods for controlling infectious diseases.


14 December

Brainard J, Jones NR, Lake IR, Hooper L, Hunter PR. Community use of face masks and similar barriers to prevent respiratory illness such as COVID-19: a rapid scoping review. Euro Surveill. 2020 Dec;25(49):2000725. PubMed: https://pubmed.gov/33303066. Full-text: https://doi.org/10.2807/1560-7917.ES.2020.25.49.2000725

Everything You Always Wanted to Know About Face Masks* (*But Were Afraid to Ask). Does wearing face masks reduce primary respiratory infection risk by only 6–15%? See also the comment by Cowling BJ, Leung GM. Face masks and COVID-19: don’t let perfect be the enemy of good. Euro Surveill. 2020 Dec;25(49):2001998. PubMed: https://pubmed.gov/33303063. Full-text: https://doi.org/10.2807/1560-7917.ES.2020.25.49.2001998


Pavelka M, Van-Zandvoort K, Abbott S, et al. The effectiveness of population-wide, rapid antigen test based screening in reducing SARS-CoV-2 infection prevalence in Slovakia. medRxiv 2020, posted 4 December. Full-text: https://doi.org/10.1101/2020.12.02.20240648

On 31 October, Slovakia deployed around 20 thousand medical staff and 40 thousand non-medical personnel to administer up to 4 million SARS-CoV-2 tests in 2 days. Here the authors report the results of the mass testing where rapid antigen tests were used to screen the whole population and to isolate infectious cases together with their household members. Prevalence of detected infections decreased by 58% (95% CI: 57-58%) within one week in the 45 counties that took part in two rounds of mass testing. See also the comments at https://www.sciencemediacentre.org/expert-reaction-to-a-pre-print-looking-at-population-wide-rapid-antigen-testing-for-sars-cov-2-in-slovakia/


12 December

Siva N. Experts call to include prisons in COVID-19 vaccine plans. Lancet 2020, published 12 December. Full-text: https://doi.org/10.1016/S0140-6736(20)32663-5

In any given week more than 200.000 people are booked into jails across the USA, and the same number leave each week. US prisons are SARS-CoV-2 hubs, says the author, “people go to court, go back to their prison, and often people get moved to another prison once they have been sentenced.” Consider prisoners an important group in vaccine prioritization.


10 December

Chan NC, Li K, Hirsh J. Peripheral Oxygen Saturation in Older Persons Wearing Nonmedical Face Masks in Community Settings. JAMA December 8, 2020. 2020; 324(22):2323-2324. Full-text: https://doi.org/10.1001/jama.2020.21905

Some people still claim on social media that masks can cause hypoxia and are therefore dangerous. Please forget this nonsense. Noel C. Chan provided participants aged 65 years or older with a 3-layer plane-shaped disposable non-medical face mask with ear loops (Boomcare DY95 model) and a portable pulse oximeter. In their cross-over study on 25 subjects, wearing a 3-layer nonmedical face mask was not associated with a decline in oxygen saturation.


8 December

Mitze T, Kosfeld R, Rode J, Wälde K. Face masks considerably reduce COVID-19 cases in Germany. Proc Natl Acad Sci U S A. 2020 Dec 3:202015954. PubMed: https://pubmed.gov/33273115. Full-text: https://doi.org/10.1073/pnas.2015954117

Face masks became mandatory at different points in time across different regions in Germany. Timo Mitze and colleagues compared the rise in infections in regions with masks and regions without masks. Weighing various estimates, they concluded that face masks reduced the daily growth rate of reported infections by around 47%.


7 December

Bahethi RR, Liu BY, Asriel B, et al. The COVID-19 Student Workforce at the Icahn School of Medicine at Mount Sinai: A Model for Rapid Response in Emergency Preparedness. Acad Med. 2020 Dec 1. PubMed: https://pubmed.gov/33264110. Full-text: https://doi.org/10.1097/ACM.0000000000003863

From March 15, 2020 to June 14, 2020, student volunteers recorded 29.602 hours (2277 hours per week) in 7 different task forces which operated at 7 different hospitals throughout the health system. Volunteers included students from all years of medical school as well as PhD, master’s, and nursing students.


Ghram A, Briki W, Mansoor H, Al-Mohannadi AS, Lavie CJ, Chamari K. Home-based exercise can be beneficial for counteracting sedentary behavior and physical inactivity during the COVID-19 pandemic in older adults. Postgrad Med. 2020 Dec 4. PubMed: https://pubmed.gov/33275479. Full-text: https://doi.org/10.1080/00325481.2020.1860394

Lockdowns, quarantine and self-isolation are periods characterized by cessation of outdoor exercise. To avoid the harmful effects of periods of not doing exercise, physical activity (PA) could be prescribed to older adults, which is of great importance for breaking their sedentary lifestyle and improving their immunity. The authors discuss the importance of performing PA to reduce the harmful effects of COVID-19.


29 November

Vogel G, Couzin-Frankel J. Grade: incomplete. Science 27 November 2020: Vol. 370, Issue 6520, pp. 1023-1027. Full-text: https://doi.org/10.1126/science.370.6520.1023

Schools around the world are again the site of a large, and largely uncontrolled, experiment. Scrutiny of school openings in countries where the virus is resurgent paints a complex picture of the risks and how they might be managed. In their well-balanced article, Gretchen Vogel and Jennifer Couzin-Frankel summarize the main questions. How common are school outbreaks? (answer: less common than initially feared, although data are sparse). Do open schools change risk perception? (answer: probably). How much fresh air is enough? (answer: we don’t know, but high-quality carbon dioxide monitors may help) Does testing make a difference? (answer: yes, but it takes up potentially scarce resources and can give a false picture). Should schools stay open as cases surge? (answer: let’s better think about what we need to do to keep schools open).


26 November

Mina MJ, Parker R, Larremore DB. Rethinking Covid-19 Test Sensitivity — A Strategy for Containment. N Engl J Med 2020; 383:e120. Full-text: https://doi.org/10.1056/NEJMp2025631

Do we really need a highly sensitive SARS-CoV-2 test? Yes, if we want to make a diagnosis of SARS-CoV-2 infection. No, if we want to prevent as many transmission events as possible. In this brilliant Perspective, Michael Mina, Roy Parker and Daniel Larremore advocate the massive use of cheap (< 5 US$) and rapid lateral-flow antigen tests which can be produced in the tens of millions or more per week, and could be performed at home. Note that lateral-flow antigen tests have limits of detection that are 100 or 1000 times higher than that of the PCR tests; however, this is largely inconsequential if your goal is to identify people who are currently transmitting SARS-CoV-2. Find out more about ‘COVID filter’, the ‘long tail of RNA positivity’ and the economic burden of thousands of people being sent to 10-day quarantines after positive RNA tests despite having already passed the transmissible stage of infection.


Gallagher JE, Sukriti KC, Johnson IG, et al. A systematic review of contamination (aerosol, splatter and droplet generation) associated with oral surgery and its relevance to COVID-19. BDJ Open 6, 25 (2020). Full-text: https://doi.org/10.1038/s41405-020-00053-2

The SARS-CoV-2 pandemic has impacted the delivery of dental care and has led to re-evaluation of infection control standards. After exploring the evidence on bioaerosols in dentistry, the authors conclude that “a risk of contamination (microbiological, visible and imperceptible blood) to patients, dental team members and the clinical environment is present during oral surgery procedures, including routine extractions.” Our recommendation: schedule your dentist appointments between COVID-19 waves.


24 November

Xu J, Xiao X, Zhang W, et al. Air-Filtering Masks for Respiratory Protection from PM2.5 and Pandemic Pathogens. One Earth Volume 3, ISSUE 5, P574-589, November 20, 2020. Full-text: https://doi.org/10.1016/j.oneear.2020.10.014

Air-filtering masks, also known as respirators, protect wearers from inhaling fine particulate matter (PM2.5) in polluted air, as well as airborne pathogens. Fibrous medium, used as the filtration layer, is the most essential component of an air-filtering mask. This comprehensive review gives an overview of the development of fibrous media for air filtration.


19 November

Bundgaard H, Bundgaard JS, Raaschou-Pedersen DET, et al. Effectiveness of Adding a Mask Recommendation to Other Public Health Measures to Prevent SARS-CoV-2 Infection in Danish Mask Wearers : A Randomized Controlled Trial. Ann Intern Med. 2020 Nov 18. PubMed: https://pubmed.gov/33205991. Full-text: https://doi.org/10.7326/M20-6817

Ammunition for your friends who deny the usefulness of wearing face masks? This Danish study finds that wearing surgical masks doesn’t really reduce the SARS-CoV-2 infection rate among wearers. Don’t read the article without reading the comment by Laine C, Goodman SN, Guallar E. The Role of Masks in Mitigating the SARS-CoV-2 Pandemic: Another Piece of the Puzzle. Ann Intern Med. 2020 Nov 18. PubMed: https://pubmed.gov/33205993. Full-text: https://doi.org/10.7326/M20-7448 and the editorial by Frieden TR, Cash-Goldwasser S. Of Masks and Methods. Ann Intern Med. 2020 Nov 18. PubMed: https://pubmed.gov/33205992. Full-text: https://doi.org/10.7326/M20-7499. And maybe we should ask researchers from South-East Asia to repeat the study.

Continue wearing face masks!


14 November

Buchan AG, Yang L, Atkinson KD. Predicting airborne coronavirus inactivation by far-UVC in populated rooms using a high-fidelity coupled radiation-CFD model. Sci Rep 10, 19659 (2020). Full-text: https://doi.org/10.1038/s41598-020-76597-y

To mitigate transmission of aerosolised SARS-CoV-2 coronavirus, we are all following one or more of three key principles: minimize time of exposure to virus (by limiting interactions), maximize distance from sources of virus (social distancing), and/or shield yourself from the virus (wear PPE). Here, the authors propose using narrow bandwidth, short wavelength UVC (207–222 nm) to mitigate further SARS-CoV-2 transmission. Their model shows that disinfection rates are increased by a further 50-85% when using far UVC within currently recommended exposure levels compared to the room’s ventilation alone. [Unlike typical UVC, which has been used to kill microorganisms but is carcinogenic and cataractogenic, recent evidence has shown that far UVC is safe to use around humans.]


31 October

Hutchins HJ, Wolff B, Leeb R, et al. COVID-19 Mitigation Behaviors by Age Group — United States, April–June 2020. MMWR Morb Mortal Wkly Rep 2020;69:1584–1590. Full-text: http://dx.doi.org/10.15585/mmwr.mm6943e4

This report of 6,475 online or telephone surveys provides four important insights into the practice of mitigation behaviors among U.S. adults to prevent the spread of SARS-CoV-2. First, the majority of U.S. adults reported engaging in most or all of the six mitigation behaviors assessed. Second, age was an important determinant of engagement in mitigation behaviors overall. A smaller percentage of adults aged <60 years, particularly those aged 18–29 years, reported engaging in the mitigation behaviors assessed compared with adults aged ≥60 years. Third, while reported use of face masks increased significantly across all age groups over time, other reported mitigation behaviors declined or did not change significantly across age groups. Finally, compared with adults who reported wearing a mask, those who did not report mask use also reported engaging in significantly fewer other mitigation behaviors during the same period, with significant declines in all other behaviors from April to June.


30 October

Chan NC, Li K, Hirsh J. Peripheral Oxygen Saturation in Older Persons Wearing Nonmedical Face Masks in Community Settings. JAMA. Published online October 30, 2020. Full-text: https://doi.org/10.1001/jama.2020.21905

Social media campaigns have claimed that masks can cause hypoxia and are therefore dangerous. (Following this reasoning, almost all surgeons would suffer from chronic hypoxia…) Consequently, concerns have emerged about the safety of wearing face masks. In this small crossover study, wearing a 3-layer nonmedical face mask was not associated with a decline in oxygen saturation in older participants.


29 October

Gallotti R, Valle F, Castaldo N, et al. Assessing the risks of ‘infodemics’ in response to COVID-19 epidemics. Nat Hum Behav 2020, published 29 October. Full-text: https://doi.org/10.1038/s41562-020-00994-6

In pandemic times, lockdown measures might need to be extended to social media (in clear: shutting down Twitter and Facebook). After analyzing more than 100 million Twitter messages posted worldwide during the early spring pandemic (from 22 January to 10 March 2020), the authors found that measurable waves of potentially unreliable information preceded the rise of COVID-19 infections and exposed entire countries to falsehoods that posed a serious threat to public health.


27 October

Denning D, Kilcoyne A, Ucer C, et al. Non-infectious status indicated by detectable IgG antibody to SARS-CoV-2. Br Dent J 229, 521–524 (2020). Full-text: https://doi.org/10.1038/s41415-020-2228-9

Dentists should know who is infectious and who is not. Here, David Denning and colleagues propose that those with a positive SARS-CoV-2 IgG antibody are non-infectious (> 99% certainty) and that a positive SARS-CoV-2 IgG antibody is therefore a much more accurate determination of infectiousness than a repeat PCR which is only 70% sensitive. The big question for 2021: will SARS-CoV-2 vaccine responses include protective IgG titers?


20 October

Lauterbach K. Will Germany’s effective Covid strategy work again as it enters a second wave? The Guardian 2020, published 19 October. Full-text: https://www.theguardian.com/commentisfree/2020/oct/19/germany-covid-second-wave-virus

The first wave taught us that if politicians and scientists work together, they have more chance of beating this virus.


15 October

Oltermann P. Berlin gives middle finger to anti-maskers in tourism agency ad. The Guardian 2020, published 14 October. Full-text: https://www.theguardian.com/world/2020/oct/14/berlin-gives-middle-finger-to-anti-maskers-in-tourism-agency-ad

An ad placed in local papers by the German capital’s senate as part of a public information campaign shows an elderly woman presenting her outstretched middle finger to the camera, next to the words: “A finger-wag for all those without a mask: we stick to corona rules.” John F. Kennedy would add: “Ich bin ein Berliner.


14 October

Macron E. Curfew in France. France 2, October 14, 8 p.m. Link: https://www.france.tv/france-2/journal-20h00/1987881-edition-du-mercredi-14-octobre-2020.html

As we disclosed yesterday (see the comment on the paper by Andronico et al, https://covidreference.com/top-10-october-13; a great thanks to our contact at the Élysée Palace!), Emmanuel Macron, the French President, has announced this evening a 9 p.m. – 6 a.m. curfew of at least four weeks. The curfew which will be in place for four weeks from midnight on Saturday, October 17, affects around 20 million people (30% of the French population) in Île-de-France (literally “Island of France”) and eight other cities (Lille, Rouen, Saint-Etienne, Toulouse, Lyon, Grenoble, Aix-en-Provence and Montpellier). A lesson of science some other countries can only dream of.


13 October

The European Union (EU) has agreed today on a traffic light system for travel amid the second COVID-19 wave. The member states will share the latest epidemiological data with the European Centre for Disease Control which will publish a map of Europe (also including data from the Schengen Associated States), updated weekly, in a variety of colours depending on the risk in a given region. There will be no restrictions if you are travelling from a “green” region. When travelling from an “orange” or a “red” region, national governments may ask you to get tested or undergo quarantine. Governments will give clear and timely information before they introduce such measures. Find more information at https://ec.europa.eu/info/live-work-travel-eu/health/coronavirus-response/travel-during-coronavirus-pandemic_en


Andronico A, Kiem CT, Paireaux J, et al. Evaluating the impact of curfews and other measures on SARS-CoV-2 transmission in French Guiana. medRxiv 2020, posted 12 October. Full-text: https://doi.org/10.1101/2020.10.07.20208314

Might curfews be a less costly alternative, both economically and socially, to complete lockdowns? In French Guiana, an overseas départment, a combination of curfews and targeted lockdowns in June and July 2020 was sufficient to avoid saturation of hospitals. On weekdays, residents were first ordered to stay at home 11 p.m., then at 9 p.m., later again at 7 p.m., and finally at 5 p.m. On weekends, everyone had to stay at home from 1 p.m. on Saturday (Andronico 2020). Whether curfews can be successfully adapted to other areas than French Guaiana, is not known. French Guaiana is a young territory with a median age is 25 years and the risk of hospitalisation following infection was only 30% that of France. About 20% of the population had been infected with SARS-CoV-2 by July 2020 (Andronico 2020). Be prepared, though, to see some curfew orders over the coming six months.


10 October

Eden E, Frencken J, Gao S, et al. Managing dental caries against the backdrop of COVID-19: approaches to reduce aerosol generation. Br Dent J 229, 411–416 (2020). https://doi.org/10.1038/s41415-020-2153-y

SARS-CoV-2 can be transmitted via aerosols – a particular concern for dentists who need to perform procedures that produce aerosol. Ece Eden et al. aim to remove or reduce the generation of aerosols during the management of carious lesions (use of high-viscosity glass-ionomer sealants, atraumatic restorative treatment, silver diamine fluoride, the Hall Technique and resin infiltration). May we give you some personal advice? If you have a problem with your teeth, fix them now! In a few weeks, it may be more difficult or less safe to get dental care.


8 October

Peeples L. Face masks: what the data say. Nature 2020, published 6 October. Full-text: https://www.nature.com/articles/d41586-020-02801-8

Face coverings save lives, either by preventing SARS-CoV-2 infection or by reducing the viral infectious load. They are not infallible (so keep your distance!), but a profoundly important pillar of pandemic control. Why is the debate still going on? Read this Nature news feature by Lynne Peeples.


28 September

Han E, Tan MMJ, Turk E, et al. Lessons learnt from easing COVID-19 restrictions: an analysis of countries and regions in Asia Pacific and Europe. Lancet 2020, published 24 September. Full-text: https://doi.org/10.1016/S0140-6736(20)32007-9

Lockdowns cannot be sustained for the long term and governments worldwide face the challenge of easing lockdowns and restrictions while balancing various health, social, and economic concerns. Now Helena Legido-Quigley, Emeline Han and colleagues examine the approaches taken by nine high-income countries and regions that have started to ease COVID-19 restrictions: five in the Asia Pacific region (i.e., Hong Kong [Special Administrative Region], Japan, New Zealand, Singapore, and South Korea) and four in Europe (i.e., Germany, Norway, Spain, and the UK). What can we learn from these experiences?


27 September

Wei Y, Ye Z, Cui M, Wei X. COVID-19 prevention and control in China: grid governance. Journal Public Health 2020, published 26 September. Full-text: https://doi.org/10.1093/pubmed/fdaa175

Grid governance is a key measure that helps to promote decentralization at the grassroots level, applied in both urban and rural communities in China. It may not be to everyone’s taste as it seeks to divide the basic level of society into many responsible grids, and accordingly it inserts affairs, organizations and people into particular grids, and also uses modern technology to comprehensively and quickly complete basic information collection. But it may have been helpful in bringing the Chinese epidemic under control. Find out more about ‘grid governance’.


19 September

CDC 20200918. Overview of Testing for SARS-CoV-2 (COVID-19). Centers for Disease Control 2020, updated 18 September. Accessed 19 September. Full-text: https://www.cdc.gov/coronavirus/2019-ncov/hcp/testing-overview.html

As has happened often this year, the US is arriving late. Yesterday, the CDC rectified their recommendations on testing. The update: any person who comes into contact with a known carrier of the virus should be tested for the virus, even if the person is asymptomatic. See also the comment by McCarthy T. CDC makes U-turn on Covid testing guidelines that prompted backlash. The Guardian 2020, published 18 September. Full-text: https://www.theguardian.com/world/2020/sep/18/cdc-guidelines-coronavirus-testing-published-despite-objection-scientists


Chia ML, Chau DHH, Lim KS. Managing COVID-19 in a Novel, Rapidly Deployable Community Isolation Quarantine Facility. Ann Intern Med 2020, published 17 September. Full-text: https://doi.org/10.7326/M20-4746

Where would you ideally accommodate low-risk COVID-19 patients? Singapore chose to implement large-scale institutional isolation units, so-called Community Care Facilities (CCFs). These massive-scale isolation facilities are a delicate balance between prioritizing safety for all and ensuring holistic patient care. Read about converting existing public spaces, augmented by telemedicine, 3758 patient admissions and close to 5000 medical consults in one month.


18 September

Zeng W, Wang X, Li J, et al. Association of Daily Wear of Eyeglasses With Susceptibility to Coronavirus Disease 2019 Infection. JAMA Ophthalmol. Published online September 16, 2020. Full-text: https://doi.org/10.1001/jamaophthalmol.2020.3906

Yiping Wei, Weibiao Zeng and colleagues describe 276 patients from Hubei Province, China, at the beginning of the pandemic. They found that the proportion of the patients who reported routinely wearing eyeglasses more than 8 hours per day (5.8%; 16 of 276 patients) was lower than in the general population (31.5%). The authors suggest that daily wearers of eyeglasses may be less susceptible to COVID-19. See also the comment by Maragakis LL. Eye Protection and the Risk of Coronavirus Disease 2019: Does Wearing Eye Protection Mitigate Risk in Public, Non–Health Care Settings? JAMA Ophthalmol 2020, published 16 September. Full-text: https://doi.org/10.1001/jamaophthalmol.2020.3909


16 September

Dubbink JH, Branco TM, Ballah Kamara KB, et al. COVID-19 treatment in sub-Saharan Africa: if the best is not available, the available becomes the best. Travel Med Infect Dis. 2020 Sep 11:101878. PubMed: https://pubmed.gov/32927051. Full-text: https://doi.org/10.1016/j.tmaid.2020.101878

Martin Grobusch, Jan Dubbink and colleagues discuss the management of COVID-19 in sub-Saharan Africa, in a context of lack of health care workers and health care infrastructure. The authors conclude that locally accessible resources should be adapted to deliver realistic solutions. The highest possible, yet realistic level of care is better than no care at all.


12 September

Silver SR, Li J, Boal WL, Shockey TL, Groenewold MR. Prevalence of Underlying Medical Conditions Among Selected Essential Critical Infrastructure Workers — Behavioral Risk Factor Surveillance System, 31 States, 2017–2018. MMWR Morb Mortal Wkly Rep 2020;69:1244–1249. Full-text: http://dx.doi.org/10.15585/mmwr.mm6936a3

Many essential workers are at risk of SARS-CoV-2 infection because their jobs require close contact with patients, the public, or coworkers. Now Sharon Silver et al. analyzed 6 occupation groups:

  1. health practitioners (licensed health care professionals except technicians/technologists)
  2. health technicians and technologists
  3. other health care support (except home health)
  4. patient and personal care aides in the home health industry (home health aides)
  5. protective services (correctional officers, police, sheriffs, patrol officers, firefighters, and their supervisors)
  6. teachers (preschool through grade 12)


and 7 industry groups:

  1. ambulatory health care
  2. hospitals
  3. nursing homes (nursing and residential care facilities)
  4. essential retail (grocery/other food stores, alcohol stores, pharmacies, and gas stations)
  5. food manufacturing
  6. transit (bus service/urban transit, taxi/limousine, postal services, and couriers/messengers)
  7. trucking


The results: A high prevalence of underlying medical conditions increases the risks for severe COVID-19 illness among home health aides, other health care support workers, and nursing home, trucking, and transit industry workers. The authors recommend that for all essential workers, and particularly those at high risk because of underlying medical conditions, exposure controls should be intensified. In addition, health care access should be optimized to prevent and treat underlying conditions.


11 September

Clipman SJ, Wesolowski AP, Gibson DG, et al. Rapid real-time tracking of non-pharmaceutical interventions and their association with SARS-CoV-2 positivity: The COVID-19 Pandemic Pulse Study. Clin Infect Dis. 2020 Sep 2. PubMed: https://pubmed.gov/32877921. Full-text: https://doi.org/10.1093/cid/ciaa1313

Is the impact of non-pharmaceutical interventions (NPIs) on SARS-CoV-2 positivity quantifiable? That’s what Sunil Solomon, Steven Clipman and colleagues tried to understand. They surveyed a random sample of more than 1,000 people to examine associations between NPI adoption and self-reported SARS-CoV-2 positivity. SARS-CoV-2 infection was negatively associated with strict social distancing (adjusted Odd Ratio for outdoor social distancing [aOR]: 0.10) and positively associated with transport use (aOR for ≥ 7 times vs. never: 4.29) and visiting a place of worship (aOR for ≥ 3 times vs. never: 16.0).


10 September

Salas RN, Schultz JM, Solomon CG. The Climate Crisis and Covid-19 — A Major Threat to the Pandemic Response. N Engl J Med 2020, 383:e70. Published 10 September. Full-text: https://doi.org/10.1056/NEJMp2022011

Will the climate crisis challenge our response to the COVID-19 pandemic? Yes, it might, reply Renee Salas, James Shultz and Caren G. Solomon. They propose short-term strategies for managing climate-related extreme events during the COVID-19 Pandemic:

  1. Extreme events (e.g., hurricanes, wildfires): evacuation and sheltering
  2. Extreme heat: remaining at home and in cool locations

Find the details in this Perspective article.


6 September

Lazzari S. Prevention. In: COVID Reference 2020.04, 4th updated edition, published 6 September. Full-text: https://covidreference.com/prevention

Lazzari S. Prevenzione. In: COVID Reference Italy 2020.04, Quarta edizione attualizzata, pubblicato il 6 settembre 2020. Testo integrale: https://covidreference.com/prevention_it

Stefano Lazzari, specialist in Public Health and Preventive Medicine, gives a 5000-word overview of the most important topic in a world without a COVID-19 vaccine: Prevention. See also the PDF of the updated 4th CR Edition (330 pages).



2 September

Vermaa S, Dhanak M, Frankenfield J. Visualizing droplet dispersal for face shields and masks with exhalation valves featured. Physics of Fluids 32, 091701 (2020). Full-text; https://doi.org/10.1063/5.0022968

Are you tempted to substitute your standard surgical masks for clear plastic face shields? Don’t, recommend Siddhartha Verma, Manhar Dhanak and John Frankenfield! Find out why widespread public use of plastic face shields could have an adverse effect on mitigation efforts.


31 August

Sauceda JA, Neilands TB, Lightfoot M, Saberi P. Findings from a probability-based survey of U.S. households about prevention measures based on race, ethnicity, and age in response to SARS-CoV-2. J Infect Dis. 2020 Aug 29:jiaa554. PubMed: https://pubmed.gov/32860499. Full-text: https://doi.org/10.1093/infdis/jiaa554

This survey in a “nationally-representative” sample of 2,029 US adults revealed that all groups engaged in the same prevention behaviors, but Whites reported being more likely to use digital tools to report/act on symptoms and seek testing, versus African Americans and Latinos. Individual behaviors may not explain COVID-19 case disparities, and digital tools for tracking should be focus on uptake among racial/ethnic minorities.


30 August

Jones NR, Qureshi ZU, Temple RJ, Larwood JPJ, Greenhalgh T, Bourouiba L. Two metres or one: what is the evidence for physical distancing in covid-19? BMJ. 2020 Aug 25;370:m3223. PubMed: https://pubmed.gov/32843355. Full-text: https://doi.org/10.1136/bmj.m3223

Physical distancing is only one part of a wider public health approach to containing the COVID-19 pandemic. But is one meter sufficient? Or should it be two, or even more? Follow Lydia Bourouiba, Nicolas Jones and colleagues on a tour about distance, ventilation, occupancy, exposure time, people-air-surface-space management and indoor space and air managements.


Bae SH, Shin H, Koo H-Y, Lee SW, Yang JM, Yon DK. Asymptomatic transmission of SARS-CoV-2 on evacuation flight. Emerg Infect Dis 2020, published 21 August. Full-text: https://doi.org/10.3201/eid2611.203353

Infected on the aircraft toilet? Dong Keon Yon and Sung Hwan Bae report data on an 11-hour flight from Milan to South Korea with 299 asymptomatic passengers. Before boarding, strict infection control procedures were implemented (physical examinations, medical interviews, body temperature checks, removal of symptomatic passengers from the flight, etc.). The authors suggest that one patient may have been infected during the flight. On the flight, she wore an N95 mask, except when she used a toilet. The toilet was shared by passengers sitting nearby, including an asymptomatic patient. She was seated 3 rows away from the asymptomatic patient. The authors discuss as most plausible explanation “that she became infected by an asymptomatic but infected passenger while using an onboard toilet”.


27 August

Blaisdell LL, Cohn W, Pavell JR, Rubin DS, Vergales JE. Preventing and Mitigating SARS-CoV-2 Transmission — Four Overnight Camps, Maine, June–August 2020. MMWR Morb Mortal Wkly Rep. ePub: 26 August 2020. DOI: http://dx.doi.org/10.15585/mmwr.mm6935e1

You can let the virus lose, but you can also control it. Here Laura Blaisdell et al. report insights from four overnight summer camps with 1,022 attendees where a multilayered prevention and mitigation strategy was successful in identifying and isolating three asymptomatic COVID-19 cases and preventing secondary transmission. Discover the meticulous planning and preparation of the camps. Perfection can be helpful in life.


19 August

Grassly NC, Pons-Salort M, Parker EPK, et al. Comparison of molecular testing strategies for COVID-19 control: a mathematical modelling study. Lancet Infect Dis 2020, published 18 August. Full-text: https://doi.org/10.1016/S1473-3099(20)30630-7

Tedros Adhanom Ghebreyesus didn’t get everything right in the SARS-CoV-2 pandemic, but he was right when he recommended: “Test, test, test!” (WHO, 16 March 2020; see also our Prevention chapter), but countries have taken different approaches and the effectiveness of alternative strategies is unknown. Now Nicolas Grassly and colleagues from the Imperial College COVID-19 Response Team investigate the potential impact of different testing and isolation strategies on SARS-CoV-2 transmission. Their conclusion: “Molecular testing can play an important role in prevention of SARS-CoV-2 transmission, especially among health-care workers and other high-risk groups, but no single strategy will reduce R below 1 at current levels of population immunity. Immunity passports based on antibody tests or tests for infection face substantial technical, legal, and ethical challenges.


16 August

Patterson EI, Prince T, Anderson ER, et al. Methods of inactivation of SARS-CoV-2 for downstream biological assays. J Infect Dis, August 15, 2020. Full-text: https://doi.org/10.1093/infdis/jiaa507

To facilitate the transfer of infectious samples from high containment laboratories, Edward Patterson and colleagues from Liverpool School of Tropical Medicine have tested methods commonly used to inactivate virus and prepare the sample for additional experiments. Incubation at 80° C, a range of detergents, Trizol reagents and UV energies were successful at inactivating a high titer of SARS-CoV-2. Methanol and paraformaldehyde incubation of infected cells also inactivated the virus. The protocols presented here can provide a framework for in-house inactivation of SARS-CoV-2.


Hatfield KM, Reddy SC, Forsberg K, et al. Facility-Wide Testing for SARS-CoV-2 in Nursing Homes — Seven U.S. Jurisdictions, March–June 2020. MMWR Morb Mortal Wkly Rep 2020;69:1095–1099. Full-text: http://dx.doi.org/10.15585/mmwr.mm6932e5

Again and again: If you have a case a nursing home, test everyone, residents and HCP, immediately. In regression analyses among 88 nursing homes with a documented case before facility-wide testing occurred, each additional day between identification of the first case and completion of facility-wide testing was associated with identification of 1.3 additional cases. Among 62 facilities that could differentiate results by resident and HCP status, an estimated 1.3 HCP cases were identified for every three resident cases.


12 August

Schünemann HJ, Akl EA, Chou R, et al. Use of facemasks during the COVID-19 pandemic. Lancet Respir Med. 2020 Aug 3:S2213-2600(20)30352-0. PubMed: https://pubmed.gov/32758441. Full-text: https://doi.org/10.1016/S2213-2600(20)30352-0

SARS-CoV-2 infected people are infectious for at least 48 h before symptom onset (pre-symptomatic); in addition, some people have only minor symptoms (paucisymptomatic) while others remain entirely asymptomatic. Will face masks protect us? Partly, yes, but will it be worth the public’s money or outweigh any potential harms? It depends, say Holger Schünemann and colleagues. In a setting with high baseline risks, such as health-care workers caring for a superspreading patient with COVID-19, wearing a mask may prevent the infection in up to one out of two health-care workers; consequently, there is a strong recommendation that all such individuals should wear a face mask, despite uncertainty in the evidence. In highly populated areas that have high infection rates—eg, USA, India, Brazil, or South Africa—the use of masks will probably outweigh any potential downsides. Read more about the sometimes difficult choices about the type of face mask, including cost, equity, acceptability, and feasibility.


Ebrahim SH, Rahmen NMM, Imtiaz R, et al. Forward planning for disaster-related mass gatherings amid COVID-19. Lancet Planet Health 2020, published 11 August. Full-text: https://doi.org/10.1016/S2542-5196(20)30175-3

Occurrences of extreme humid heat, higher than the optimal human survivability limit of 35° C, have more than doubled in frequency since 1979, leading to an increased frequency of tropical cyclones. Ziad Memish and colleagues now explain that all disasters cause large-scale population movements – making physical distancing in the new COVID-world almost impossible. If you are involved in disaster planning, discover all the details you need to keep in mind.


11 August

Lazzari S. Prevention. In: COVID Reference 2020.04, 4th updated edition, published 11 August. Full-text: https://covidreference.com/prevention

Stefano Lazzari, specialist in Public Health and Preventive Medicine, gives a 5000-word overview of this most important topic in a world without a COVID-19 vaccine. See also the PDF (320 pages) of the updated Fourth CR Edition.


Ramírez-Cervantes KL, Romero-Pardo V, Pérez-TovarC, et al. A medicalized hotel as a public health resource for the containment of Covid-19: more than a place for quarantining. J Public Health 2020, published 10 August. Full-text: https://doi.org/10.1093/pubmed/fdaa129

Karen Lizzette Ramírez-Cervantes and colleagues describe the implementation of a medicalized hotel in Madrid for the containment of COVID-19. Between March and 9 May 2020, 399 patients were admitted; 59% (235) were migrants; the main reason for referral (58%) was a lack of housing conditions for quarantining, including overcrowding. The hotel provided medical care and housing to a subgroup of a vulnerable population who could not afford a safe quarantine.


8 August

Budd J, Miller BS, Manning EM, et al. Digital technologies in the public-health response to COVID-19. Nat Med 2020, published 7 August. Full-text: https://doi.org/10.1038/s41591-020-1011-4

Your review for the weekend – seven pages and 151 references will give you a glimpse of how the digital world might fight back to SARS-CoV-2. Rachel McKendry and colleagues critically review how billions of mobile phones, low-cost computing resources and advances in machine learning and natural language processing are being recruited into a gigantic antiviral network.


Firth JA, Hellewell J, Klepac P, et al. Using a real-world network to model localized COVID-19 control strategies. Nat Med 2020, published 7 August. Full-text: https://doi.org/10.1038/s41591-020-1036-8

Lewis Spurgin and colleagues simulate control strategies for SARS-CoV-2 transmission in a real-world social network generated from high-resolution GPS data that were gathered in the course of a citizen-science experiment. They find that tracing the contacts of contacts reduces the size of simulated outbreaks more than tracing of only contacts and suggest that contact tracing and quarantine might be most effective as ‘local lockdown’ strategies when contact rates are high.


Schilling K, Gentner DR, Wilen L, et al. An accessible method for screening aerosol filtration identifies poor-performing commercial masks and respirators. J Expo Sci Environ Epidemiol 2020, published 7 August. Full-text: https://doi.org/10.1038/s41370-020-0258-7

During the initial phases of the COVID-19 pandemic the shortage of regulation-tested masks contributed to the rapid spread of SARS-CoV-2 in healthcare settings. Here Lisa Lattanza and colleagues present experimental methods to evaluate mask filtration and breathability via cost-effective approaches that could be easily replicated in communities without extensive infrastructure.


6 August

Aleta A, Martín-Corral D, Pastore y Piontti A, et al. Modelling the impact of testing, contact tracing and household quarantine on second waves of COVID-19. Nat Hum Behav 2020. Published 5 August. Full-text: https://doi.org/10.1038/s41562-020-0931-9

Some countries are currently facing second-wave scenarios. To understand the challenges ahead, Yamir Moreno, Esteban Moro, Alessandro Vespignani and colleagues integrated anonymized and privacy-enhanced data from mobile devices and census data and built a detailed agent-based model of SARS-CoV-2 transmission in the Boston metropolitan area. They found that a period of strict social distancing followed by a robust level of testing, contact-tracing and household quarantine could keep COVID-19 within the capacity of the healthcare system while enabling the reopening of economic activities.


4 August

Krueger A, Gunn JK, Watson J, et al. Characteristics and Outcomes of Contacts of COVID-19 Patients Monitored Using an Automated Symptom Monitoring Tool — Maine, May–June 2020. MMWR Morb Mortal Wkly Rep 2020, published 3 August. Full-text: http://dx.doi.org/10.15585/mmwr.mm6931e2

A prompt case investigation can rapidly identify contacts and recommend quarantine, reducing additional exposures and transmission. Here Anna Krueger and colleagues present 1,622 contacts of 614 COVID-19 patients who were enrolled in an automated symptom monitoring system in May and June 2020. 190 (11.7%) eventually developed COVID-19. The authors conclude that using digital tools in support of a comprehensive contact tracing strategy can make the contact tracing and monitoring process faster and more efficient.


31 July

National Academies of Sciences, Engineering, and Medicine. Reopening K-12 Schools During the COVID-19 Pandemic: Prioritizing Health, Equity, and Communities. The National Academies Press 2020. Washington, DC (accessed 31 July 2020). Full-text (download free PDF as guest): https://doi.org/10.17226/25858

How will schools reopen in the context of rapidly changing patterns of community SARS-CoV-2 spread (Dibner 2020)? Now the US National Academies of Sciences, Engineering, and Medicine provide a series of recommendations aimed at helping states and school districts determine both whether to open school buildings for in-person learning and, if so, how to reduce risk in the process of reopening (Reopening K-12 Schools During the COVID-19 Pandemic: Prioritizing Health, Equity, and Communities). Read also the comment by Dibner KA, Schweingruber HA and Christiakis DA. Reopening K-12 Schools During the COVID-19 Pandemic. JAMA 2020, published 29 July. Full-text: https://doi.org/10.1001/jama.2020.14745


Auger KA, Shah SS, Richardson T, et al. Association Between Statewide School Closure and COVID-19 Incidence and Mortality in the US. JAMA. 2020 Sep 1;324(9):859-870. PubMed: https://pubmed.gov/32745200. Full-text: https://doi.org/10.1001/jama.2020.14348

Was the closure of primary and secondary schools in the US associated with a decreased incidence and mortality of COVID-19? According to Katherine Auger and colleagues, it was: COVID-19 62% lower; deaths 58% lower. States that closed schools earlier, when cumulative incidence of COVID-19 was low, had the largest relative reduction in incidence and mortality. The authors caution that some of the reduction may have been related to other concurrent non-pharmaceutical interventions. See also the comment by Donohue JM, Miller E. COVID-19 and School Closures. JAMA 2020, published online July 29. Full-text: https://doi.org/10.1001/jama.2020.13092


27 July

Gallagher J, Johnson I, Verbeek J et al. Relevance and paucity of evidence: a dental perspective on personal protective equipment during the COVID-19 pandemic. Br Dent J 229, 121–124 (2020). Full-text: https://doi.org/10.1038/s41415-020-1843-9

Dentists and their staff are among the most exposed health care professionals to SARS-CoV-2 infection. The authors apply a recently updated Cochrane review (see below, Verbeek et al.) of personal protective equipment (PPE) and examine evidence on which type of full body PPE and what methods of putting on or taking off full body PPE are most effective.

Verbeek JH, Rajamaki B, Ijaz S, et al. Personal protective equipment for preventing highly infectious diseases due to exposure to contaminated body fluids in healthcare staff. Cochrane Database Syst Rev. 2020 May 15;5:CD011621. PubMed: https://pubmed.gov/32412096. Full-text: https://doi.org/10.1002/14651858.CD011621.pub5


Parker S, Mahomed O. Hypoxia and Thrombosis in COVID-19: New Considerations for Air Passengers. Journal of Travel Medicine 2020, published 25 July. Full-text: https://doi.org/10.1093/jtm/taaa122

The authors recommend pre-boarding as well as on-board pulse oximetry screening for early detection of silent hypoxia, especially in unwell passengers boarding long-haul commercial flights.


22 July

Sehgal AR, Himmelstein DU, Woolhandler S. Feasibility of Separate Rooms for Home Isolation and Quarantine for COVID-19 in the United States. Ann Intern Med. 2020 Jul 21. PubMed: https://pubmed.gov/32692931. Full-text: https://doi.org/10.7326/M20-4331

SARS-CoV-2-infected and -exposed persons are instructed to separate themselves from others to limit further spread through droplets and aerosol produced by coughs, sneezes, singing or even talking. But what if separate bedrooms and bathrooms are unavailable? The sober finding of the authors: more than 80 million persons in the US (about 1 in 5) live in places that are not suitable for isolation or quarantine.


13 July

Rodriguez-Martinez CE, Sossa-Briceño MP, Cortés-Luna JA. Decontamination and reuse of N95 filtering facemask respirators: a systematic review of the literature. Am J Infect Control. 2020 Jul 8:S0196-6553(20)30690-8. PubMed: https://pubmed.gov/32652253. Full-text: https://doi.org/10.1016/j.ajic.2020.07.004

Again, put your masks in the sun. But not too often as at higher UV dosages and cycles, strengths of the material can be reduced. The maximum number of cycles under different conditions is still unclear. However, among 14 studies reporting on the different decontamination methods that might allow disposable N95 FFRs to be reused, ultraviolet germicidal irradiation (UVGI) and vaporized hydrogen peroxide (VHP) seem to be the most promising decontamination methods for N95 FFRs. This is based on their biocidal efficacy, filtration performance, fitting characteristics, and residual chemical toxicity, as well as other practical aspects such as the equipment required for their implementation and the maximum number of decontamination cycles.


5 July

Patrício Silva AL, Prata JC, Walker TR, et al. Rethinking and optimising plastic waste management under COVID-19 pandemic: Policy solutions based on redesign and reduction of single-use plastics and personal protective equipment. Sci Total Environ. 2020 Jun 30;742:140565. PubMed: https://pubmed.gov/32622168. Full-text: https://doi.org/10.1016/j.scitotenv.2020.140565

The amount of waste generated due to COVID-19 indeed threatens the existing waste management streams, meaning that plastic leakage/pollution may impose severe risks to both environmental and human health. Thus, it is imperative to increase monitoring (aquatic, terrestrial and aerial surveys) of plastic waste under post-COVID-19, around the world. This paper provides an overview of plastic policies and discusses the readjustments of these policies during the COVID-19 pandemic along with their potential environmental implications. Policy recommendations and future research directions are also discussed.


18 June

Lyu W, Wehby GL. Community Use Of Face Masks And COVID-19: Evidence From A Natural Experiment Of State Mandates In The US. Health Aff (Millwood). 2020 Jun 16. PubMed: https://pubmed.gov/32543923. Full-text: https://doi.org/10.1377/hlthaff.2020.00818

Masks, masks, masks. This study provides evidence from a natural experiment on the effects of state government mandates in the US for face mask use in public issued by 15 states plus DC between April 8 and May 15. Mandating face mask use in public was associated with a decline in the daily COVID-19 growth rate by 0.9, 1.1, 1.4, 1.7, and 2.0 percentage-points in 1–5, 6–10, 11–15, 16–20, and 21+ days after implementation, respectively. Estimates suggest as many as 230,000–450,000 COVID-19 cases possibly averted by May 22, 2020 due to these mandates.


17 June

Cai C, Floyd EL. Effects of Sterilization With Hydrogen Peroxide and Chlorine Dioxide on the Filtration Efficiency of N95, KN95, and Surgical Face Masks. JAMA Netw Open. 2020 Jun 1;3(6):e2012099. Full-text: https://doi.org/10.1001/jamanetworkopen.2020.12099

This quality improvement study found that the sterilization process had different effects on the filtration efficiencies of different masks. Sterilization with H2O2 had fewer negative effects than ClO2.