COVID Transmissions for 7-23-21

Delta is among the most infectious respiratory viruses

Jul 23, 2021

Greetings from an undisclosed location in my apartment. Welcome to COVID Transmissions, now entering its second year.

It has been 614 days since the first documented human case of COVID-19. In 614, during the Byzantine-Sasanian war, a joint Jewish-Persian army liberated the city of Jerusalem, conquered from the Jews by the Romans centuries earlier. This didn’t last, but it is a moment of note in the history of struggle against Roman Imperialism.

Today we’ll discuss a few stories about the Delta variant, including the CDC director’s recent comments that this variant is among the most infectious respiratory viruses. Also, we’ll discuss attempts to estimate the true COVID-19 death toll in India.

Despite all the worrying stories about COVID-19, please remember: it’s the weekend in summer, where a lot of fun can be had outside safely. Try to enjoy it!

Bolded terms are linked to the running newsletter glossary.

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Now, let’s talk COVID.

CDC Director calls Delta variant one of the most infectious respiratory viruses known

Yesterday, CDC Director Dr. Rochelle Walensky called the Delta variant of COVID-19 one of the most infectious known respiratory viruses. As far as I can tell, this is indeed true.

It thus makes us ask the question: what induced this? The answer is, clearly, that it’s uneven global measures to counteract the pandemic. When some portion of the population tries hard to be protected, while others do not, a system of evolutionary incentives is set up to encourage a virus to spread more effectively. If measures were followed aggressively and with widespread adherence, this would not be able to happen because the barrier created would be too high. But in places where the response is uneven, and some people try to protect themselves while others do not, a surmountable barrier is created. The virus lineages that are best at transmitting during brief interactions, that increase their window of transmissibility, and that improve the likelihood that an infectious dose is delivered in some way—these are the ones that survive to replicate.

This situation will continue, with increasing pressure selecting for more infectious viruses, until enough people are immune or taking other measures to prevent infection—or both—to make for an insurmountable barrier. There really isn’t a way, though, that we can stop evolution from happening—short of eradicating the virus—but if we remove the pathway that selects for more transmissible versions, then it will be forced to go in a different direction. For example, if the only people that the virus infects are vaccinated ones, this just might select for variants that can spread without causing symptoms. Something like that would be great; that would mean COVID-19 stops being nearly so much of a threat.

Effectiveness of one vs two vaccine doses against Delta variant

Early on in the news arc about Delta, I shared a preprint that indicated that single-dose vaccination with a two-dose vaccine is insufficient to provide reasonable protection against COVID-19 caused by this virus variant. That preprint has matured into a published paper, with revised figures: https://www.nejm.org/doi/full/10.1056/NEJMoa2108891

It looks like single-dose vaccination drops to around 30% effective when Delta is the variant doing the infecting. This underscores, as the original preprint did, that it’s important to get fully vaccinated as soon as possible.

Estimating the uncounted deaths in India’s most recent COVID-19 spike

I want to thank Carl Fink for suggesting this story.

One of the biggest problems in pandemics is uneven healthcare surveillance—particularly in countries with large populations that have challenges with health infrastructure. One of the countries on that list early in the pandemic was a little place called the United States. US surveillance eventually got better, but there is still a presumed undercounting in the US.

In India, where official figures suggest that about 411,000 people died of COVID-19, the undercount is apparently particularly extreme. Several news sources, including Business Insider, have done roundups on recent estimates of the true number: https://www.businessinsider.com/indias-true-covid-19-death-toll-2021-7?op=1

All of the estimates related there get into the millions. While it is numerically estimable, on an emotional level, that is a truly incalculable loss of life. Get vaccinated!

What am I doing to cope with the pandemic? This:

Catching up with an old mentor

Last night, my wife and I got dinner with an old scientific mentor of mine, who really got me my start as a scientist. If anyone reading this is an aspiring scientist, or knows someone who is, I really recommend trying to reach out to a scientist—even if it’s someone you don’t know—and trying to see if they need some volunteer help. Academic labs work on a shoestring, meaning they often need some extra help, and having connections in the academic world from early on can make a huge difference in an overall career. I got my start as a volunteer in this way; all it took was asking, followed by about a decade of hard work afterwards.

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