"Airborne transmission of COVID-19: The controversy" Topic

Orac, aka, Dr David Gorski MD's take on the airbone transmission of COVID-19.

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One of the biggest mysteries early on in the COVID-19 pandemic that continues to some extent even today is how SARS-CoV-2, the coronavirus that causes COVID-19, spreads. While it's always been known to spread primarily through respiratory droplets (and that is still thought to be the primary method of spread), there are still so many questions that remain. For instance, you might remember that early on in the pandemic, fomites (objects on which virus-laden respiratory droplets could land and thereby harbor the virus) were thought to be a major source of infection, as people would touch such objects and then touch their face, and no doubt many of you remember all the breathless stories in March about studies showing that SARS-CoV-2 could survive up to three days on plastic and metal surfaces and up to 24 hours on cardboard. Then, a month ago, the CDC published a news release and updated its website to say that indirect contact from a surface contaminated with coronavirus is a potential way to contract COVID-19 but not the most prominent way that the virus infects people, emphasizing that the "primary and most important mode of transmission for COVID-19 is through close contact from person-to-person" and stating that fomite transmission is not "thought to be the main way the virus spreads." None of this makes it any less of a good idea or any less imperative that you wash your hands frequently and avoid touching your face. The virus can still spread that way; it's just not the primary driver of infection. The real debate though bubbled up in the news over the 4th of July weekend in the form of a story in The New York Times entitled "239 Experts With 1 Big Claim: The Coronavirus Is Airborne":

The World Health Organization has long held that the coronavirus is spread primarily by large respiratory droplets that, once expelled by infected people in coughs and sneezes, fall quickly to the floor.

But in an open letter to the W.H.O., 239 scientists in 32 countries have outlined the evidence showing that smaller particles can infect people, and are calling for the agency to revise its recommendations. The researchers plan to publish their letter in a scientific journal next week.

Even in its latest update on the coronavirus, released June 29, the W.H.O. said airborne transmission of the virus is possible only after medical procedures that produce aerosols, or droplets smaller than 5 microns. (A micron is equal to one millionth of a meter.)

Proper ventilation and N95 masks are of concern only in those circumstances, according to the W.H.O. Instead, its infection control guidance, before and during this pandemic, has heavily promoted the importance of handwashing as a primary prevention strategy, even though there is limited evidence for transmission of the virus from surfaces. (The Centers for Disease Control and Prevention now says surfaces are likely to play only a minor role.)

The text of the letter can be found here.

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Reading the news stories and the letter, I thought of two things. First, the reaction to this story reminds me of the reaction to stories that have emerged regarding how presymptomatic and asymptomatic COVID-19 patients can spread coronavirus to others. The second—and more relevant—thing was that this debate reminded me of a very similar debate that I wrote about nearly six years ago. At the time, the nation was gripped in fear that the deadly Ebola virus would make its way here from Africa in order to cause outbreaks, and there was a similar question: Could Ebola be spread by air? Because I've written about this before, it allows me to expand a bit on the same basic concepts that I discussed in the context of Ebola and discuss them in the context of what we know about COVID-19. I'll be very straightforward in admitting that I don't know yet what to believe on this question, but I'll look at the basic concepts and the evidence.

I'm not sure what the point is here.

I'm not sure what the point is here

I'm not sure what the point is here.

Final paragraph:

The information gathered on these characteristics of SARS-CoV-2, how it spreads, and how it causes disease will then be of use in the study of other respiratory viruses and future pandemics. In the meantime, I'm coming to the conclusion that we should assume that respiratory aerosol is a major mode of spread of COVID-19 and act accordingly. In many ways, we are already doing that, as social distancing and masks are primary means of preventing the transmission of viruses transmitted this way. However, more can be done, particularly in buildings. Additional strategies to mitigate the spread of COVID-19 in buildings could include refreshing stale indoor air, passing recirculated air through a high-efficiency filter to prevent infecting people in adjacent rooms, and other means of keeping airborne virus confined to limited areas. Then, as the science comes in, recommendations can be fine-tuned based on what we learn. In the meantime, there is no reason to be any more alarmed or even, in most cases, to change what we're doing to protect ourselves and others.