The Most Likely Way You Can Catch COVID-19

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In March we posted a video of the good Dr. Jeffrey VanWingen bringing groceries into the home. Remember this guy?

His video was viewed over 26 million times, and scared the crap out of us as we left packages outside in our garages, and disinfected items one by one, trying to keep ourselves and our loved ones safe from coronavirus.

Six months have passed and while we still feel like we’re stumbling through the pandemic, we’ve learned a lot since March. One thing we’ve learned is that much of what we did with our groceries in March was unnecessary.

Surfaces don’t matter so much

Scientists originally thought we’d catch the virus from surfaces because that’s how scientists and epidemiologists think most respiratory diseases are spread. Early studies showed how long the virus would live on surfaces, sometimes days. But those studies relied on an unrealistic amount of virus being spewed onto surfaces from the droplets we cough, sneeze, and breath onto door handles, door knobs and other high touch surfaces.

“You would have to have 100 people coughing and sneezing on one small area of surface to get the amount of virus that was used in the papers that reported the survival of the virus on surfaces.”

 Emanuel Goldman, PhD, a professor of microbiology and biochemistry at Rutgers University

Scientists have also learned that the SARS-CoV-2 virus is quite fragile compared to other viruses, and dries up rather quickly. In the real world, a normal amount of virus on a surface is likely to be completely gone in a day, as it gradually reduces by half in a six hour period.

This doesn’t mean that you can’t get it from surfaces, but a very specific set of events would have to occur for that to happen. Keep washing your hands so that they don’t reach your face with virus on them, but we don’t have to disinfect our groceries.

Close range droplets are the new leading theory

In May, the CDC updated their guidelines to say that fomites, or surfaces, were not a major source of transmission. The droplets that come from our noses and mouths are more infective in the air than they are on a surface. Sneezing, coughin, singing, talking, shouting, and even breathing pushes these droplets out at a 3-6 foot distance. The heaviest particles drop quickly, the lighter droplets stay afloat longer.

Being in close contact with someone raises the risk that you’ll be exposed to the small droplets they’re expelling, and many scientists now think that’s how most people become infected with the virus. One reason is that a virus inside a freshly exhaled droplet is more likely to be alive and infectious than a virus that’s been sitting on a doorknob for several hours. The other reason is that, in close range, breathing in the air that someone else just breathed out is going to expose you to a higher quantity of virus particles — called the inoculum — than after the droplets disperse and fall to the ground.

If you stay more than six feet from others, it’s unlikely you will come into contact with these droplets carrying the virus. With this in mind, most people catch the virus from someone they live with. However there are documented cases where people caught the virus while remaining distance from others, as well as hamster studies that show the animals, while separated, caught the virus by being in the same room.

Aerosol transmission is gaining acceptance

Scientists are reluctant to say the virus is airborne, as most viruses are not. Measles and chickenpox are highly contagious, so scientists accept that these diseases are likely to be airborne. By comparison, the novel coronavirus is not nearly as contagious. Each person with SARS-CoV-2 will likely spread it to 2 or 3 people. A person with measles will spread it to 15 others.

In July over 200 scientists convinced the WHO that it was possible that SARS-CoV-2 was airborne. Scientists still don’t know exactly how much of the novel coronavirus is needed to make someone sick, but it’s likely higher than conventional airborne viruses.

The number of viruses needed to make someone sick is still unanswered, along with the question of how long the virus can live in the air. Because viruses can dry up rather quickly in smaller particles, many are not considered airborne. Some scientists point to live virus having been collected from the air in Covid-19 patient hospital rooms as a “smoking gun” on the subject, but there are no peer-reviewed studies yet.

How to protect yourself from all transmission routes

While no one knows for sure the dominant route of transmission, scientists agree it’s likely to be some range of both droplet and aerosol transmission. In either event, the proper protection is the same for both methods: wear a mask and keep your distance.

Evidence of the importance of masks, in particular, has been mounting, not only because they trap outgoing particles from escaping, which protects others, but also because they block larger incoming particles from getting into a person’s airways, protecting the mask wearer themselves. And even if some viral particles do get through, the viral dose will still be much smaller, so the person will be less likely to get seriously ill.

Aerosol transmission increases the importance of ventilation and air filtration. Introducing fresh air into a room or adding filtration to the air can help dilute and disperse existing airborne particles. Being outdoors is the ultimate in ventilation, but with colder weather coming, indoor filtration and mask wearing will be even more important.

So this fall and winter, instead of buying more sanitizing products, consider investing in an air purifier, more comfortable two-ply cloth masks, or a fire-pit or outdoor heater. Meet friends outside, and if you have people in your home, insist on masks. And don’t worry about sanitizing your groceries.

From Medium.

Additional sources:

Los Angeles Times, Hopkins Medicine