Coronavirus Update: New Developments on COVID-19

It’s been a couple months since I did a post explicitly about COVID-19, or SARS-COV2, or coronavirus, and since the pandemic is still happening and is on everyone’s mind, I’m going to do another one today. This time, I’m going to do a big picture look at where we stand on transmission risks, reinfections, immunity, and what I think we need to keep in mind as we go forward.

Where do we stand with coronavirus?

How is it transmitted—and how can we avoid it?

What’s the deal with herd immunity?

What are my thoughts on the biggest challenges yet to come?

What’s the riskiest place to be?

Indoor areas with low air circulation. Things seem to be spiking in hot areas where everyone stays indoors blasting the air conditioning and breathing in recycled air because it’s so damn hot outside. In regions where people get out into hot weather, like Hawaii, the virus is virtually non-existent. There are certainly other factors at play—Hawaii is an island protected by thousands of miles of water, for one, and they have a strict quarantine protocol for visitors—but many transmissions have been linked to indoor areas with AC.

Furthermore, all indications are that it’s harder to get infected from a “glancing blow.” Viral load—the number of viral particles you actually take in — is a big factor. If the initial load is small enough, your immune system has a better chance of fighting it off. If the load is too big, your immune system can get overwhelmed. What’s “too big” a load is different for everyone, but all else being equal, a larger viral load is worse. That’s why health care workers who spend a lot of time around infected patients are at a greater risk. But if you’re passing someone on the street? It’s going to be a much lower risk.

Is coronavirus easy to transmit outdoors?

I asked about this on Twitter the other day, wondering if anyone had good evidence of outdoor transmission. There were many responses. Some of the more notable ones.

• A 4th of July beach party in Michigan. Hundreds of people standing close together in knee high water, lots of house boats, “several” cases of coronavirus. There was also a house party a couple hundred miles away the same weekend that produced 40 cases. The indoor house party was much more virulent than the outdoor beach party.
• A Memorial Day party at the Lake of the Ozarks in Missouri. Very crowded, looked iffy. One attendee ended up with coronavirus, but officials haven’t identified any other positive cases linked to the party. I wasn’t able to find any recent updates to the contrary. The outdoor lake party didn’t seem very dangerous in this instance.
• No cases detected after the July 4th speech at Mount Rushmore. They could still pop up, given the potential lag time between exposure and symptoms, but it looks good so far.
• There were also transmission cases after an outdoor graduation event and indoor prom on the same weekend. 19 students tested positive. All students attended both events, so it’s hard to determine if the cases occurred at the graduation event (which probably had indoor parties afterward) or at the prom (or both).

An earlier Chinese study found that out of 7,300 instances of person-to-person transmission, only one occurred outdoors.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7327724/‘>² Researchers searched through PubMed, media stories, and any other legitimate reports on transmission events and found that the vast majority of transmissions occurred indoors.

This is good news, if it holds. It means people can feel a little safer about going outside, getting sunshine, getting physical activity, and living their lives. Avoid crowds and wear a mask when you’re around people, but I’m cautiously optimistic that being outdoors is the safest place to be.

Does COVID-19 spread through breathing?

This has always been the great fear. Does the virus spread through aerosol from simple breathing, talking, or are sneezes, coughs, and yelling required? Are aerosolized viral particles enough? Or do we need larger droplets?

A new pre-print just came out that has people worried. They took breath samples from symptomatic COVID-19 patients, found live viral particles in the aerosolized droplets, and found they could replicate on isolated human cells.https://www.nature.com/articles/s41586-020-2550-z‘>⁴ In another study, between 20-50% of unexposed people showed t-cell activity against COVID-19.