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'Stealth Transmission' of COVID-19 Demands Widespread Mask Usage

Eldad Einav, MD
March 29, 2020

Last Saturday, my local hospital reached a sad milestone: We had our first COVID-19 death.

I am a staff cardiologist at the hospital in Binghamton, New York, and like hospitals everywhere, we have been anticipating a surge in patients. Personal protective equipment (PPE) is in short supply and is being rationed. We are encouraged to reuse disposable equipment multiple times, and access to surgical masks is limited.

The epidemic is overwhelming the healthcare system, and clinicians are essential regardless of specialty. As I considered my own high risk for exposure, I reviewed existing protective measures that could keep me from contracting the virus and further transmitting it to my coworkers, family, and especially to my elderly father who resides with me.

I was concerned to see that most healthcare workers (HCWs) and patients are still roaming the hospital floors and the emergency department without wearing masks. Hospitals are citing guidelines from the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) restricting mask use mostly to close encounters with symptomatic individuals or confirmed cases with COVID-19.

I decided to research the evidence and justification behind official prevention guidelines. My findings were rather striking.

It is widely agreed that face masks (even surgical masks and non-fit-tested respirators) are an effective barrier against COVID-19, as its primary mode of transmission is through respiratory droplets. Contrary to common belief, however, respiratory droplets are released not only when sneezing or coughing, but also when talking.

Still, the CDC strongly discourages mask use in the community or by healthcare workers when not directly exposed to a symptomatic individual. The message from authorities is clear: Among asymptomatic individuals, masks are not effective against the spread of COVID-19. In fact, facing a nationwide shortage of masks, the surgeon general tweeted, "STOP BUYING MASKS!"

To be clear, mask use is one of the most effective physical interventions to prevent the spread of respiratory viruses. A comprehensive Cochrane review examined multiple physical preventive measures (eg, screening at entry ports, isolation, quarantine, social distancing, barriers, personal protection, hand hygiene) and found that masks were the most consistent and comprehensive measure.

So why not recommend universal usage, for HCWs and the community alike?

The main reason given by authorities is that there is no evidence showing that it is effective in the community. However, "there is an essential distinction between absence of evidence and evidence of absence," write Hong Kong scholars in a comment in The Lancet. The paucity of data regarding widespread mask use does not mean that masks are not effective.

In a striking contrast to prevention guidelines in the Western world, Asian countries such as China, Japan, South Korea, and Hong Kong have made masks a cornerstone of their strategy in fighting the pandemic. China has even enforced compulsory face mask policies in some regions.

The rationale against mask use in the community partially relies on the premise that people without symptoms don't spread the virus. But this view is changing as new data are accumulated. Even the CDC has acknowledged reports of asymptomatic and presymptomatic transmission: "Some spread might be possible before people show symptoms ... but this is not thought to be the main way the virus spreads."

A study published in the New England Journal of Medicine evaluated a group of returning travelers from Wuhan, China, to Frankfurt, Germany. The researchers discovered "that shedding of potentially infectious virus may occur in persons who have no fever and no signs or only minor signs of infection."

Asymptomatic transmission was also estimated in multiple modeling studies of the outbreak. A study published in the journal Science shows that "nondocumented infections were the infection source for 79% of documented cases." Jeffrey Shaman, the lead author, stated that this "stealth transmission" is flying under the radar and becoming a major driver of the epidemic.

Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, expressed similar views and urged health authorities to "tell the public what we know and don't know."

As the weight of evidence shifts toward supporting a major role for asymptomatic transmission, the use of personal facemasks, especially in crowded areas, becomes instrumental in preventing community spread of the virus. We can no longer rely on symptoms or screening to tell us whether mask protection is needed.

So why voice a need for widespread mask use in desperate times when we do not even have enough masks for hospitals?

The reason is that by making the facts public, more resources may become available. The message that masks not only can protect healthcare workers but also can help control the outbreak may recruit more efforts, allocate more resources, and make this a national top priority.

This was exactly what happened in Asia, where universal mask wear has been advised. Both Taiwan and South Korea faced shortages of masks, and they responded by increasing mask production. Taiwan opened 60 new productions at various manufacturing plants across the country to produce 10 million masks a day.

The same can be done in the United States. Resources can be mobilized to fill that need. The president has the power to order the industry to produce more masks by further executing the Defense Production Act. In the meantime, homemade cloth masks could be used in the community, similar to CDC advice to HCWs "when no facemasks are available." Limited data suggest that cloth masks protect against droplet transmission better than no barrier.

As new infections soar across the country, authorities should share emerging data regarding COVID-19 transmission clearly, even if complete understanding is still evolving and despite low availability of PPE.

Eldad Einav is a clinical assistant professor at SUNY Upstate Medical University who focuses on cardiometabolic health.

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Reviewed on 3/30/2020
References
SOURCE: Medscape, March 29, 2020.

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