These three new papers should not be overinterpreted. Only one of them has been vetted by peer review at this point. It also remains unclear, and undemonstrated, whether the Covid-19 virus released from patients’ lungs comes out in aerosol form; whether aerosolized particles of this virus travel significant distances; and, if so, whether they do so in sufficient number to cause infection. Notably, while the joint WHO-China mission report published in late-February said that although airborne particles were “not believed to be a major driver of transmission,” it noted that such a mode “can be envisaged if certain aerosol-generating procedures are conducted in health care facilities.”
Given that much research on airborne transmission in outbreaks is focused on medical settings, it’s also less than clear how even the most common viruses might pass from person to person under everyday circumstances. Julian Tang and his colleagues have created a visualization of the breaths exchanged by two people in conversation standing three feet apart. Most of the time, the puffs of air they let out remain separate; but portions of their exhalations do sneak from each person’s breathing space into the other’s. Given all this uncertainty, some experts say there needs to be better public messaging on the spread of the new coronavirus. “Crowded public transport where people can breathe on each other may also lead to transmission of infection,” Tang says, echoing public-health advice that, while widespread, may not be getting as much emphasis as hand-washing. Milton agrees, adding that it might be wise to shut off air-recirculation systems in cars, which could potentially spread the pathogen among passengers.
Even if it turns out that the new coronavirus is meaningfully airborne, at least in rare circumstances, you shouldn’t rush out to buy masks, including N95 respirators. Don’t do that. We’ve already witnessed grave shortages of masks for health workers and people who are immunocompromised. To buy one now is to put those people’s lives in danger.
The scientists I spoke with for this story do not want people to shutter themselves inside in fear of toxic vapors. They point out that being outdoors, in fresh air exposed to UV light, is healthy. They do not want to encourage anyone to cower from all social interaction. This article is not meant to induce panic among the worried well, who clog health systems needed for people who are actually ill. But there needs to be a more nuanced understanding of this issue.
When public health officials say a pathogen is or isn’t “airborne,” they create a false dichotomy that doesn’t keep people safe. In this particular case, the folks who are most at risk for airborne transmission are medical workers. Just this week, amidst concerns about insufficient supplies of respirators, the US Centers for Disease Control and Prevention updated its guidance for healthcare personnel dealing with the Covid-19 pandemic. Based on its assertion that “airborne transmission from person-to-person over long distances is unlikely,” the agency said that “facemasks”—presumably the floppy surgical masks that do not do as much to protect against floating pathogens—constitute an acceptable alternative for healthcare workers. (It does note that N95s should be prioritized for procedures that are especially likely to release virus into the air.) But if the JAMA study and preprint articles from this week prove correct, and the new coronavirus falls somewhere on the spectrum of airborne-ness besides not at all, then this advice might be counterproductive.
When it comes to this virus’s ability to travel in air—in hospitals or elsewhere—it’s hard to know where things will ultimately land. Until then, describing it in absolute terms seems risky.
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