This Week in the Pandemic, September 24, 2020

So this week, I saw 2 separate suggestions of herd immunity from people who have medical degrees, several headlines about how the coronavirus is mutating, and an alarming chart from somewhere in the United States. Let’s consider them in order.

“Herd Immunity”

This is a concept that’s been discussed a lot, I think since Day 1 of the pandemic in the U.S. Of note this week, Rand Paul, who has a medical degree and ought to know better, indicated that he thinks New York has already achieved herd immunity. It would be great to know where he’s getting (or not getting) his data, or how he’s arrived at his estimate of herd immunity, but we’ll come back to that.

First, let’s talk about herd immunity. In general it means that enough people are immune to an infection that the infection is effectively unable to transmit within that group. Herd immunity is the goal of most immunization campaigns. What people have never really striven for, however, is herd immunity through natural infection. Throughout history, at least in the hundreds of books, stories, and articles I’ve read, humans have never opted to let an epidemic run rampant in pursuit of herd immunity. Some level of herd immunity in historic pandemics was achieved, but that was a byproduct of being unable to prevent infection rather than a societal goal.

Why is that?

A) The death toll would probably be catastrophic.

B) We don’t know that immunity will happen.

Immunity to any virus or bacterial infection isn’t guaranteed. It’s plausible that infection with this coronavirus will give a person some level of immunity, but we don’t know that for sure so it’s best to do what we can to slow the spread of the infection. That gives us time to find treatments and develop a vaccine.

Also, herd immunity is a phenomenon of small groups. What do I mean by that? Let’s pretend there’s a mythical city called Herdville. In Herdville there are 10,000 people. Out of those 10,000 people 9,000 of them have developed immunity to coronavirus and 1,000 have not. At 90% immunity, they should have achieved herd immunity, right? Well, those 1,000 non-immune Herdvillites have a weekly picnics to commiserate about being non-immune. One day, a visitor from Virustown comes through and stops at the picnic to ask for directions. The Herdvillites are so welcoming that the Virustown visitor decides to stay a while. He’s infected with coronavirus and 10 of the non-immune people get infected. At next week’s picnic, the virus continues to spread through people who don’t have symptoms or don’t remember to stay home. Suddenly there’s an outbreak in a place that thought they’d had herd immunity.

New York is a big place so there may always be pockets of people where outbreaks occur, even for well-controlled diseases. But New York had a rough time early in the pandemic, in March and April this year. So have they had enough infections to reach herd immunity? Here’s what we know.

1. New York City has had about 250,000 cases.

2. New York City has 8,300,000 residents

3. That means 3% of people in New York City have been confirmed as infected.

(Sources: https://www.nytimes.com/interactive/2020/us/new-york-coronavirus-cases.html#county, https://www.census.gov/quickfacts/newyorkcitynewyork)

Now, there are certainly people who have been infected that aren’t counted in the case count. Let’s say there are 10 times as many people who have been infected, so then maybe 30% of New Yorkers. That’s way at the low end of any reasonable estimate for herd immunity.

So why have there been so few cases in New York lately? Because they’re taking precautions to prevent infections. People are probably staying away from each other, limiting their gatherings and social interactions, wearing masks in crowded areas, getting tested when they have symptoms, adhering to quarantine measures and, in general, listening to public health recommendations.

The moral of the story: Just because case counts are low doesn’t mean there is herd immunity.

“Is SARS-CoV-2 mutating?”

Headlines blared “coronavirus mutating” or “evolving” this week. And they say that makes it “more contagious” so you should run for the hills! The sky is falling! https://www.washingtonpost.com/health/2020/09/23/houston-coronavirus-mutations/?arc404=true https://uk.reuters.com/article/uk-health-coronavirus-mutation/houston-study-more-contagious-coronavirus-strain-now-dominates-idUKKCN26E3KK

Sorry for the hyperbole, but words like “mutating” and “contagious” can be scary and that’s probably why it’s in the headline. Keep in mind, though, that all viruses constantly evolve (in fact, all organisms constantly evolve). It’s just the way biology works on Earth (and probably elsewhere).

In the context of coronavirus, the question is whether or not it’s something to be concerned about. The answer, I think, is Yes and No. Yes, we should be concerned about possible mutations. No, we shouldn’t be as concerned about the mutation as we should be about the pandemic. The “mutation” most of these articles are talking about has been in place for several months. A new study published this week found that the “mutated” version is more common. If you want to learn more about this, I recommend this podcast from The Naked Scientists. They talk about mutations around 20 minutes in. https://www.thenakedscientists.com/podcasts/naked-scientists-podcast/where-did-covid-come

The bottom line is that this version of the virus may be better at infecting people but it’s far from clear whether or not this will make much difference in the pandemic.

So, what do we do? The same thing we’ve been doing for several months: limit your interactions with other people, wash your hands often when you go out, wear a mask in crowded areas (to protect others from your germs), get tested if you have symptoms, stay home when you’re sick.

“Alarming Chart”

Finally, there’s this chart from the Wisconsin Department of Health Services. What the hell, Wisconsin?!?!

But perhaps more concerning on the world scale, is India, where about 90,000 people have been diagnosed each day for the past 2 weeks. Let’s hope they can slow it down.