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HomeCoronavirusMask wearing effectiveness, including among asymptomatic COVID-19 carriers

Mask wearing effectiveness, including among asymptomatic COVID-19 carriers

 

The two hair stylists in Springfield, Missouri, broke the cardinal rule of infection control: STAT News reports that despite having respiratory symptoms, one went to work and saw clients for eight days, when she learned she had tested positive for COVID-19. Her colleague also developed symptoms, three days after her co-worker, and also kept working until she tested positive, two days after the first stylist. Together, they saw 139 clients, with appointments for haircuts, shaves, and perms lasting 15 to 45 minutes.

Yet, the report says, when the local health department identified and contacted the 139 clients, asking them to self-quarantine for 14 days and checking in daily about whether they had developed COVID-19 symptoms, not a single one (of the 104 who agreed to be interviewed) did. Of the 67 who consented to a swab test, every one tested negative.

STAT News points out there was one other notable fact about the case: Both stylists and every client had worn a face covering.

The report says the stark case, described by researchers at Washington University School of Medicine at St Louis, University of Kansas Medical Centre, Springfield-Greene County Health Department and CoxHealth Infection Prevention Services in a Morbidity and Mortality Weekly Report, adds to the near-universal scientific consensus that, more than any of single action short of everyone entering solitary confinement, face coverings can prevent the transmission of the coronavirus that causes COVID-19.

“Like herd immunity with vaccines, the more individuals wear cloth face coverings in public places where they may be close together, the more the entire community is protected,” Robert Redfield, director of the US Centres for Disease Control and Prevention, and two colleagues wrote in an editorial.

Because cloth face coverings can also allow states to more safely ease stay-at-home orders and business closings, Redfield told a JAMA Live webcast Tuesday, “If we could get everybody to wear a mask right now, I really think in the next four, six, eight weeks, we could bring this epidemic under control.”

The “if,” of course, has been the problem, the report says. Because masking or refusing to mask has become a political statement, only 62% of Americans said in April that they did so (the CDC recommended the practice on April 3); in May, 76% said they did. The CDC advice followed weeks of mixed and contradictory messaging, and even after it was issued, President Trump and other national leaders fell well short of endorsing face coverings.

Although mask wearing does not differ by gender, it does vary by region of the country. In May, 87% of people surveyed in the Northeast said they wore masks when going out in public; it was 80% in the West, 74% in the Midwest, and 71% in the South, where cases are skyrocketing.

Face coverings almost certainly explain why the Springfield hair stylists did not transmit the virus to a single client. Of the 104 clients surveyed, 102 said they wore a face covering (usually cloth coverings or surgical masks) during their entire appointment; two said they did for part of it. Both stylists were always masked.

The report says the benefits of masking in reducing viral transmission are clear from much more than the unusual case of a Springfield hair salon, of course. In an unpublished analysis of 194 countries, those that did not recommend face masks saw per-capita COVID-19 mortality increase 54% every week after the first case appeared; in countries with masking policies, the weekly increase was only 8%.

And at the largest health care system in Massachusetts, Mass General Brigham, before administrators adopted a policy of universal masking for health care workers in late March, new COVID-19 infections in that population were increasing exponentially, from 0% to 21%, or 1.16% per day, on average, researchers reported in another paper. With everyone masked, the rate of COVID-19 in health care workers fell to 11.5% by late April, dropping 0.49% per day, on average.

In his editorial, Redfield made not only a public health case for face coverings but also an economic one. Citing an analysis by Goldman Sachs Research, he and his colleagues noted that if masking increased 15%, it “could prevent the need to bring back stay-at-home orders that would otherwise cost an estimated 5% of gross domestic product, or a projected cost of $1trn.”

“Broad adoption of cloth face coverings is a civic duty,” Redfield and his co-authors wrote in their editorial.

MMR Report summary
What is already known about this topic?
Consistent and correct use of cloth face coverings is recommended to reduce the spread of SARS-CoV-2.
What is added by this report?
Among 139 clients exposed to two symptomatic hair stylists with confirmed COVID-19 while both the stylists and the clients wore face masks, no symptomatic secondary cases were reported; among 67 clients tested for SARS-CoV-2, all test results were negative. Adherence to the community’s and company’s face-covering policy likely mitigated spread of SARS-CoV-2.
What are the implications for public health practice?
As stay-at-home orders are lifted, professional and social interactions in the community will present more opportunities for spread of SARS-CoV-2. Broader implementation of face covering policies could mitigate the spread of infection in the general population.

Authors
M Joshua Hendrix; Charles Walde; Kendra Findley; Robin Trotman

Abstract
The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has severely affected health care workers (HCWs).1 As a result, hospital systems began testing HCWs2 and implementing infection control measures to mitigate workforce depletion and prevent disease spread.3 Mass General Brigham (MGB) is the largest health care system in Massachusetts, with 12 hospitals and more than 75 000 employees. In March 2020, MGB implemented a multipronged infection reduction strategy involving systematic testing of symptomatic HCWs and universal masking of all HCWs and patients with surgical masks.4 This study assessed the association of hospital masking policies with the SARS-CoV-2 infection rate among HCWs.
Methods: The institutional review board of MGB approved the study and waived informed consent. Using electronic medical records, we identified HCWs providing direct and indirect patient care who were tested for SARS-CoV-2 with reverse transcriptase–polymerase chain reaction between March 1 and April 30, 2020. The primary criterion for testing HCWs in our health care system was having symptoms consistent with SARS-CoV-2 infection. Information on the job description of each HCW was obtained by linking their record to the MGB Occupational Health Services and Human Resources databases.
We identified 3 phases during the study period: a preintervention period before implementation of universal masking of HCWs (March 1-24, 2020); a transition period until implementation of universal masking of patients (March 25–April 5, 2020) plus an additional lag period to allow for manifestations of symptoms (April 6-10, 2020), as previously defined5; and an intervention period (April 11-30, 2020). Positivity rates included the first positive test result for all HCWs in the numerator and HCWs who never tested positive plus those who tested positive that day in the denominator. For each HCW, any tests subsequent to their first positive test result were excluded. Using weighted nonlinear regression, we fit the best curve for the preintervention and intervention periods (based on R2 value). The number of daily tests was used as the weight such that days with more tests had more weight in determining the curve. The overall slope of each period was calculated using linear regression to estimate the mean trend, regardless of curve shape. The change in overall slope between the preintervention and intervention periods was compared to determine any statistically significant change in mean trend, using a 2-sided α = .05. The analysis was conducted using R version 4.0 (R Foundation).
Results: Of 9850 tested HCWs, 1271 (12.9%) had positive results for SARS-CoV-2 (median age, 39 years; 73% female; 7.4% physicians or trainees, 26.5% nurses or physician assistants, 17.8% technologists or nursing support, and 48.3% other). During the preintervention period, the SARS-CoV-2 positivity rate increased exponentially from 0% to 21.32%, with a weighted mean increase of 1.16% per day and a case doubling time of 3.6 days (95% CI, 3.0-4.5 days). During the intervention period, the positivity rate decreased linearly from 14.65% to 11.46%, with a weighted mean decline of 0.49% per day and a net slope change of 1.65% (95% CI, 1.13%-2.15%; P < .001) more decline per day compared with the preintervention period (Figure).
Discussion: Universal masking at MGB was associated with a significantly lower rate of SARS-CoV-2 positivity among HCWs. This association may be related to a decrease in transmission between patients and HCWs and among HCWs. The decrease in HCW infections could be confounded by other interventions inside and outside of the health care system (Figure), such as restrictions on elective procedures, social distancing measures, and increased masking in public spaces, which are limitations of this study. Despite these local and statewide measures, the case number continued to increase in Massachusetts throughout the study period,6 suggesting that the decrease in the SARS-CoV-2 positivity rate in MGB HCWs took place before the decrease in the general public. Randomized trials of universal masking of HCWs during a pandemic are likely not feasible. Nonetheless, these results support universal masking as part of a multipronged infection reduction strategy in health care settings.

Authors
Xiaowen Wang; Enrico G Ferro; Guohai Zhou; Dean Hashimoto; Deepak L Bhatt

 

[link url="https://www.statnews.com/2020/07/14/if-everyone-wore-mask-covid19-could-be-controlled-cdc-director-urges/"]STAT News report[/link]

 

[link url="https://www.cdc.gov/mmwr/volumes/69/wr/mm6928e2.htm?s_cid=mm6928e2_w"]Morbidity and Mortality Report[/link]

 

[link url="https://jamanetwork.com/journals/jama/fullarticle/2768532?"]JAMA editorial[/link]

 

[link url="https://jamanetwork.com/journals/jama/fullarticle/2768533"]JAMA abstract[/link]

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