We believe that the lack of emphasis placed on the prevention of aerosol droplet transmission is a major contributor to the rising case numbers in many areas of our country.

As intensive care unit specialists in New York City, we are concerned about the increasing rates of COVID-19 infection, which may once again overwhelm our hospitals, in parts of the United States.

The severity, morbidity and mortality of COVID-19 must be re-emphasized to all, both young and old, as it spares neither. To avoid a catastrophic repeat of the initial surge, we recommend a population-wide intervention — a significant increase in the use of N95 masks — that might allow for a safer reopening of the U.S economy.

SARS-CoV-2 was thought to be primarily transmissible via large fluid-filled droplets generated by coughing or sneezing. Those droplets usually travel short distances before falling and will not reach another person practicing social distancing nor penetrate standard (cloth or surgical) masks

However, it has recently been determined that a major mode of transmission of SARS-CoV-2 is via aerosol droplets, exhaled by presymptomatic, asymptomatic or symptomatic persons. These small aerosol particles remain airborne indoors for extended periods and can infect those nearby who inhale them into their lungs.

We believe that the lack of emphasis placed on the prevention of aerosol droplet transmission is a major contributor to the rising case numbers in many areas of our country.

What can be done to prevent the inhalation of these aerosols and therefore reduce the spread of SARS-CoV-2? The only mask that can prevent aerosol-size droplet inhalation is an N95.

Should there be widespread use of N95 masks by the general public? Not necessarily.

In Germany, Hong Kong, South Korea and Taiwan, COVID-19 was brought under control using standard masks (surgical or cloth, often homemade), an approach that relied on the fact that nearly 100% of citizens wore them in close-quartered public spaces.

Too few Americans wearing masks

Here is the key: Standard masks, although only partially effective in blocking inhalation of aerosols compared with the near perfect blocking performance of medical grade N95 masks used in hospitals, are highly effective at trapping the large droplets exhaled by infected people.

These large particles downsize to aerosol size after emission when they undergo evaporative loss. Although standard masks are imperfect in both blocking or trapping, their combined performance when worn by both infected and noninfected persons leads to a low likelihood of transmission.

The key point is that, for standard masks to be effective, there needs to be near universal wearing of these masks by all persons when in any poorly ventilated, air-recirculated, confined indoor, or highly congested outdoor environment. Conversely, emphasizing mask wearing in fresh air outdoor settings has no epidemiologic support and thus makes little sense.

Unfortunately, in some parts of the United States, the proportion of citizens routinely wearing standard masks in at-risk environments is nowhere near what's required to prevent spread. The fact that the maximal exhaled viral load of infected persons occurs before the development of actual symptoms should concern all who might come into close indoor proximity with maskless presymptomatic “super spreaders.”

How should individuals protect themselves from infection in areas where near universal indoor mask use is not the norm? In such a situation, the best option is to wear an N95, which is designed to prevent inhalation of more than 99% of all droplets, large or small.

The United States has traditionally placed an emphasis on the rights of individuals. We respect the right of, but do not agree with, our fellow citizens who choose not to wear a mask. We also, however, are perplexed as to why responsible people would choose not to wear a mask given the potential harm, including death, that they could cause to their fellow citizens.

For those who live in an area where there is a high level of mask use, the risk of transmission or acquisition of COVID-19 infection is greatly reduced. For those who live in an area where there is a low level of standard mask use, the best approach for those who choose to wear a mask is to use an N95 mask to protect themselves from inhaling the exhaled aerosol droplets of their nonmasked neighbors.

Those who protect themselves with an N95 mask would be able to safely participate in many activities involving groups of people. At-risk social gatherings and entertainment venues would be appropriate targets for routine N95 use, if universal standard mask wearing is not a precondition for entry.

'Super-spreader events' prove deadly

The scientific and media publications describing “super-spreader events” provide some of the most damning evidence of the risks of congregating without universal mask wearing:

►The choir practice where one singer infected 52 of the other 60 attendees? Aerosol transmission.

►The 22-year-old presymptomatic man who sang karaoke in an air-conditioned room for two hours and infected six of his 15 friends? Aerosol transmission.

►The presymptomatic 29-year-old man who infected 102 people during visits to multiple crowded nightclubs? Aerosol transmission.

►Cruise ship and aircraft carrier mini epidemics? Aerosol transmission through air-recirculation systems.

►The more than 100 meat-packing plants with massive outbreaks despite the workers’ wearing safety goggles, gloves and frocks? Aerosol transmission.

The challenge we face as a country is that we do not yet have sufficient N95 masks even for health care workers, let alone for widespread distribution. It is unclear to us why this is the case, as it is well within the immense industrial capacity of the United States to ramp up national production of these simple low-tech safety devices. 

Our current infection control strategies are unlikely to succeed. The public health approach will fail due to the imbalance between tracing and testing resources compared with the large and increasing number of documented and undocumented infections.

The “lockdown” approach employed by the Chinese government to rid Wuhan of the virus is not feasible in the open democracy of our country. Waiting for “herd immunity” would result in widespread death and disability while again overwhelming our hospitals. 

While we wait for a vaccine, an effective cure, or the unlikely event that all 50 states will pass public health laws that mandate universal mask wearing in all indoor public places, could we have a national initiative to ramp up production of N95 masks so that all Americans have access to this level of protection? 

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