This was originally a Facebook post of mine from 2021-7-21, and is archived here as a curiosity. Minor changes to formatting, as well as basic copy-edits, may have been made in the transition from Facebook post to web format.
Time for the July covid check-in. When the month began, we were averaging about 14,000 detected cases of the virus per day. We're now seeing more like 38,000 per day, and for the last two weeks, the number of cases per day has been rising at about 50 or 60% per week. That's an incredibly fast pace.
It's fast enough that another five weeks of 50% growth would land us at about 285,000 detected cases per day, a higher rate of infection than even during the highest surge so far. That's not to say that those numbers will happen. Either those numbers will happen within five weeks, or within five weeks the spread of the virus will slow. There's no third option.
Now, even if the numbers hit new records when it comes to cases, that doesn't mean that we will hit new records with deaths. Back in the winter, we topped out at about 3400 deaths per day. The IHME Model is thinking we'll stabilize at about 500-600 deaths per day, in October and November. While it's hard to say whether they've got the future right until we get there, it is reasonable to think the deaths will not reach the old highs. About 90% of those over 65 are already vaccinated, so the continued spread is concentrated especially among young people, who tend to take the virus a lot better.
What is happening now is that a new variant of the coronavirus, which people are calling Delta, has spread to become the virus in about 80% of American cases. Delta is a lot like the older strains of Covid, and it's susceptible to the same vaccines for the most part, but it's better at spreading.
The increased number of people catching Covid now does not change the fact that we appear to be in the endgame of the pandemic still. We can run the numbers like so. There are around 328 million Americans, and 187 million have been vaccinated, leaving about 141 un-vaccinated. Not all the unvaccinated are vulnerable -- many of these people already had covid. A reasonable guess is that perhaps half of the unvaccinated have already had the virus. That leaves -- these are all very rough numbers, but the picture is true even if the exact numbers don't hold -- maybe 70 milion susceptible people.
How many people need to reach immunity in order to reach herd immunity? We don't actually know, but estimates have ranged from 60-90% of the population. But by the time 90% are immune, it's generally agreed across the board that this would end the widespread movement of the virus through the population. When we're 90% immune, we'd still have 33 million susceptible people.
A rough estimate, then, is that we might have another 47 million people to go before we're basically done with the virus and all that's left are rare small clusters of people catching it. How long would it take to go through 47 million people? Right now, the IHME model estimates that a little over 1 million people are catching the virus, while about 1.5 million are receiving their first shot each week. So that's about 2.5 million receiving immunity per week.
At that rate, we would hit herd immunity in November, though of course it could be sooner or later than that. If the virus spreads much more widely, as it looks like it will, then that would bring on herd immunity faster. If the virus stops spreading effectively, then we've probably already reached herd immunity.
The clock is ticking in either case. The virus will either race through the remaining non-immune population, bringing this thing to an end, or it will slow down considerably. It's mathematically impossible for it to go on like this very long, at least so long as no variants have been found which evade immunity.
Sources
For basic Covid statistics -- most of the ones here -- the CDC Covid Data Tracker.
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