- Aerosol transmission is the worst thing about the novel coronavirus, as it allows the virus to linger in the air and travel long distances indoors.
- Official guidance from health organizations like the WHO and CDC still says COVID-19 spreads mainly via saliva droplets.
- Experts on aerosols put together an incredibly comprehensive guide that explains why COVID-19 aerosols are so important to acknowledge, and why face masks and good ventilation are needed to stop aerosols.
- The data presented by this guide reminds us why being indoors around other people this winter is the next big hurdle in our ongoing battle against the novel coronavirus.
Nine months into the novel coronavirus health crisis and the world is still not out of the woods. Several countries are bracing for the coronavirus second wave, which might coincide with the flu season this winter. The US appears to be heading into a third wave, as the number of daily cases started climbing again in September after a gradual decline that started after the mid-July peak. Some worry that the next peak might be even worse than either of the first two, which is incredible considering how bad things were in the first two waves.
Health experts, including Dr. Anthony Fauci, remind us over and over again about the public health measures that can help people reduce the risk of transmission. Washing hands frequently, maintaining social distance, using face masks, and avoiding crowded places indoors can all reduce the spread COVID-19. It’s not just one thing that helps, but the combination of these factors. That’s because the coronavirus is incredibly infectious and can spread with ease through the air.
Saliva droplets that are ejected during coughs and sneezes can spread in the air and contaminate the surfaces they land on. But it’s the smaller droplets that turn into aerosols that you really need to worry about. Aerosols can linger in the air for longer periods of time and travel longer distances than we previously thought. That’s the worst thing about the coronavirus and one that’s still not properly addressed by health organizations. This is why a team of researchers put together an extensive guide that explains exactly what the risks are when it comes to coronavirus aerosols.
The World Health Organization (WHO) reluctantly acknowledged the airborne spread of COVID-19 when 239 scientists urged the health body to do so. But the WHO still sees droplets as the main transmission risk. The Centers for Disease Control and Prevention (CDC) recently published and then pulled guidelines about the aerosolized spread of the SARS-CoV-2, saying they were published by mistake.
All this prompted a few aerosol experts from various fields to put together a 57-page document available online in for free via Google Docs. The document contains several chapters that explain in great detail how COVID-19 is transmitted, what aerosol spread is, and what the risks are for several scenarios — like taking a cab, going to school, or flying on an airplane.
The document also explains the type of protection we have against aerosol transmission, and that’s where face masks come in. The researchers discuss several types of masks and use cases for each of them. Ventilation is also a big part of the story. Allowing air to circulate would move the aerosols faster and reduce the risk of transmission. That’s one reason why the risk of catching COVID-19 outdoors is minimal compared to the risk indoors. The document also explains the history of aerosol transmission and why the CDC and WHO are reluctant to address airborne transmission.
Jose-Luis Jimenez is a chemistry professor at the University of Colorado who has studied aerosols for 20 years. He partnered with nine other experts to put together this comprehensive guide about COVID-19 aerosol transmission to compensate for inaction at the WHO and CDC.
Jimenez told MIT Technology Review that he’s been answering aerosol-related questions via email and social media for a while, and people’s questions are often the same. Other experts have said the same thing, so they all decided to combine their research and make it available online in one place. The advantage of having the document shared via Google Docs is that it can be updated with pertinent information in real-time. The scientists say they avoided the traditional routes in order to prevent delays from medical journals. Publishing a study would also prevent them from making changes and updates quickly.
“When we saw it was useful, we made it public. We update the document all the time,” he said. “We’re effectively having to be a little WHO or CDC. We’re saying the things that they should be saying. This is frustrating, but it’s the situation we find ourselves in. These organizations have been flat-out refusing to consider if aerosol transmission is important, which leaves people unprotected. So we feel it’s our duty to communicate directly with the public.”
Even if you don’t read the document in full, Jimenez did provide a great takeaway in his interview with MIT Technology Review, likening aerosol transmission to cigarette smoke:
The thing people need to understand is aerosol transmission is like everyone breathing out cigarette smoke, and you want to breathe in as little of others’ as possible. Everyone you are around, imagine they are breathing smoke, and try to avoid it. It’s not good enough to just give people guidelines; you need to explain the actual science behind it, too.
Avoiding aerosols is a lot like avoiding smoke, with the difference between the two being that you can actually smell smoke. Everyone should aim to breathe in as little air as possible from other people — face masks and ventilation are the best way to achieve that goal when indoors:
The second most important thing is the recommendations section—how to interpret the science for any given situation. Avoid anything that involves breathing in a lot of other people’s breath. Do things outdoors. But the most important things are free. Wear the mask you already have when you are inside public spaces, and open a window. If we did those, transmission would go down dramatically. Things like ventilation and air filtering matter, but the main things we can do cost nothing.