[jMyles]

It's strange to call this an "alternative explanation", since it's the one that expert infectious disease researchers, nearly without exception, are pointing to.

The (let's face it, silly) notion that masks and distancing suppressed all respiratory pathogens except one is a theory with very little traction, and which will almost certainly not stand up to serious scrutiny.

[bigbillheck]

> The (let's face it, silly) notion that masks and distancing suppressed all respiratory pathogens except one is a theory with very little tracti

Are you familiar with the concept of "R0" and that one virus may be more transmissible than another?

Flu has an R0 of about 1.5, and whatever covid's is, it's higher (last I saw was 2.5).

If we postulate that masking and distancing and similar measures act to reduce these numbers across the board, say by 0.6, that brings flu down to 0.9 and covid to 1.9. Outbreaks don't tend to stay around when their R0 is below 1, which would explain why there's hardly any flu this year and plenty of covid.

Source: I was trained as a mathematical biologist and did a bunch of work with compartmental models: https://en.wikipedia.org/wiki/Compartmental_models_in_epidem...

In this admittedly over-simplified model, beta is (per wiki) "the average number of contacts per person per time, multiplied by the probability of disease transmission in a contact between a susceptible and an infectious subject".

Social distancing reduces the average number of contacts, masking reduces the probability of transmission, and both act to reduce beta. You reduce beta, you reduce R0, you win.

[addicted]

There’s nothing silly about a novel virus having greater abilities to overcome barriers when compared to other pathogens that humans have had years decades and centuries to develop defenses again.

At the end of the day it’s likely gonna be the result of a combination of all these factors.

[ryankemper]

> There’s nothing silly about a novel virus having greater abilities to overcome barriers when compared to other pathogens that humans have had years decades and centuries to develop defenses again.

This isn't really quite accurate though. Before SARS-CoV-2 ever emerged, our immune systems already had defenses against it. This is because of the already-extant circulating hCoVs.

This is why something like 80% of blood samples taken before SARS-CoV-2 emerged showed T-cell cross-reactivity. From the perspective of our immune system, it was never a "novel" virus. It was novel to scientists and politicians but not to the human immune system.

[jMyles]

> There’s nothing silly about a novel virus having greater abilities to overcome barriers when compared to other pathogens that humans have had years decades and centuries to develop defenses again.

Agreed! What you are describing is viral interference: population-level immune responses to one respiratory pathogen causing suppression of others.

We've seen selective suppression of influenza and all of the other four endemic coronaviruses, while SARS-CoV-2 has thrived. This is true throughout the world, including places where stringent horizontal interdictive measures were taken, in places where no such measures were taken, and in all places in between.

> At the end of the day it’s likely gonna be the result of a combination of all these factors.

I think it's very unlikely - almost impossibly so - that interdiction has played a meaningful role in population-level suppression. I don't think it will be a combination; I think it will be explained by the same clearly observed phenomenon which has been responsible for similar outcomes in the past.

[ketzo]

Sure, viral interference, yes; but I didn’t go inside a restaurant for 13 months. You’re saying that (and masking, and social distancing in general) didn’t affect influenza transmission?

Why would it not?

[ravenstine]

Fortunately, there's data on this.

https://www.cdc.gov/mmwr/volumes/70/wr/mm7010e3.htm?s_cid=mm...

Although COVID-19 is definitely more virulent than influenza, it doesn't seem reasonable to just jump to the conclusion of saying "it must be the restrictions". That's definitely part of the equation, and maybe it will turn out to be the entire equation, but we don't know.

> During the study period, states allowed restaurants to reopen for on-premises dining in 3,076 (97.9%) U.S. counties. Changes in daily COVID-19 case and death growth rates were not statistically significant 1–20 and 21–40 days after restrictions were lifted. Allowing on-premises dining at restaurants was associated with 0.9 (p = 0.02), 1.2 (p<0.01), and 1.1 (p = 0.04) percentage point increases in the case growth rate 41–60, 61–80, and 81–100 days, respectively, after restrictions were lifted (Table 2) (Figure). Allowing on-premises dining at restaurants was associated with 2.2 and 3.0 percentage point increases in the death growth rate 61–80 and 81–100 days, respectively, after restrictions were lifted (p<0.01 for both). Daily death growth rates before restrictions were lifted were not statistically different from those during the reference period, whereas significant differences in daily case growth rates were observed 41–60 days before restrictions were lifted.

This is one hell of a virus, but if what we are seeing is that it still spreads quite rapidly even with all the restrictions, yet the flu, which is also quite virulent, manages to disappear, then I don't think we really have all the facts as to why it has gone away. Maybe it is just that simple?

I guess what I'm saying is that it's a bit concerning just how fast people here are willing to jump to conclusions.

[disgrunt]

> I guess what I'm saying is that it's a bit concerning just how fast people here are willing to jump to conclusions.

Well, the CDC/WHO have kind of conditioned them, no? The CDC, at least, is starting to realign their guidelines with the data.

[dragonwriter]

Yeah, and even in places with no mandatory measures, people would widely take voluntary measures against SARS-CoV-2 that would also be effective against other respiratory viruses.

[throwBlankie]

Whether lockdowns/restrictions are "effective" is somewhat conjecture, but likely had an effect. It's also likely that given the global and nearly total nature of this observed phenomenon that other forces are at play such as the competition and immunity stimulus mentioned in OP.