In the current surge, the current daily new case count is only about 12% of what it was a month ago. Why is this variant receding so dramatically all of a sudden?
Japan had something similar happen with their surge last summer, and I thought maybe it was just their vax rate ramping up and achieving viable herd immunity. At the time of their peak in late August, 56% of Japan had had at least one dose; a month later, they were up to nearly 70%. Seemed like a reasonable explanation.
But here in the US during our current Omicron surge, at the time of the peak in mid-January, we had 75% of the population vaxed with at least one dose. A month later, we’re now at…76.6%. Not much higher.
There have been a lot of cases of Omicron in the US, probably averaging about half a million a day since this surge started around Christmas. But that adds up to only about 25 million cases or so, less than 8% of the population. Between that and all the vaxed folks, has the disease really run out of fresh meat to infect? I would have expected the decline from the peak to be much more gradual, but it’s coming down awfully quick. This is great, but it’s puzzling.
That’s always been my understanding. You forgot to add people with at least some immunity due to already having Covid, and possibly folks who are just naturally immune. Plus lots of folks who have been infected that we don’t even know about. That could be me and my family, for all I know. I mean, this is what the scientists were predicting in December, no? I remember everyone saying everything should precipitously plummet in February.
In general, epidemics end as quickly as they begin. Omicron spreads fast, so it ramped up quickly, which also meant that it spread through the vulnerable population quickly, and burned out quickly.
I recall early in the pandemic, before Delta anyway, there some news stories reporting that the percentage of symptomatic Covid cases was maybe ~20% of total cases. Here’s a report from the University of Chicago dated May 2021, for instance.
Combine that with 1) a lot of people not getting tested or seeking treatment when they feel sick (especially the mask- and vaxhole types) and 2) some communities – like mine ()-- not reporting positive cases if the sick person self reports rather than tests at an actual clinic using a PCR test, I suspect the number of infections is some very large percent greater than the actual numbers that are reported.
Given that, the virus will, as the OP so eloquently put it, “run out of meat”. The exponential growth we saw in January was simply unsustainable.
If people totally ignored case counts and mixed randomly with the whole population and everyone experienced the disease the same, I believe you’d see a totally symmetrical rise and fall as formerly sick people became immune or died and were no longer susceptible. In reality it’s a little more complex, and behavior changes tend to spread the tail out further, but the more easily a disease spreads, the less effective behavior changes are. Omicron spreads very quickly, so you get something that’s closer to a symmetrical rise and fall than you did with earlier variants where masks and limiting contact were more effective.
There is a relationship between the ease of transmission and the rate of increase in infection. The more easily the germ infects the next hosts, the more quickly the infection rate increases.
Fortunately, another general principle is that infectious diseases tend to become less deadly as they evolve. So if a virus is less likely to kill its host right away, the better its chances are of being transmitted to the new hosts.
Therefore, more people get infected, and the number of people to be infected gets lower to the extent that the virus has trouble finding new hosts.
As a student in biostatistics, we used epidemic and pandemic data from the past to explore and confirm these principles. So far, COVID has fit the predicted evolution. The big question remaining concerns the virulence of the next evolutionary development of the virus. It is here to stay, and I think it will be like the flu with new versions popping up, and subsequent vaccine being developed. Hopefully the new variants will be relatively mild.
I hope that things ARE going to get better because of few left to get infected, less virulent forms, etc.
One big factor: It’s been a cold January and February, so after the holiday get togethers and resultant ramp up of cases, people stayed indoors and there were few gatherings.
Every local doctor on the news is warning that now is no time to let up on precautions.
Now we will see what happens as states drop mask mandates and warmer weather hits.
Interesting timing. The Colorado state Health Dept. just put out an update on the declining case numbers.
Modeling estimates that 1.4%, or 1 in every 69 Coloradans, was infectious as of Feb. 13, and 90% of Coloradans are now immune to omicron infection and even more are protected against severe disease.
)-- not reporting positive cases if the sick person self reports rather than tests at an actual clinic using a PCR test, I suspect the number of infections is some very large percent greater than the actual numbers that are reported.