The likely explanation is that, because the flu is significantly less transmissible than COVID, even states with "no restrictions" were able to knock it out because enough people took enough measures to protect themselves from airborne/surface communicable disease in general.

In other words, you can probably beat back the flu significantly by having enough of the population mask up, wash/sanitize their hands, etc.

I remember it not being a huge deal to have a bunch of people at work come with flu-like symptoms. "It's just something going around." Work gave out flu shots every year but that isn't 100%. It wasn't even considered much of a faux pas to show up to work feeling a little ill. Now, showing up to work with flu-like symptoms could put you in the hot seat with HR. Having a bunch of people fall ill in the office now results in it being closed for the day for cleaning. It won't stay this way forever but it's going to be a while until most people go back to being lax on contagious diseases. Imagine companies forcing employees and schools forcing students to mask up during flu season.

I really, really hope that "coming to work sick" is considered bad form from now on, or even outright against policy.

It's always been dumb: at best they're just getting more people sick (some of whom will need to take time off, negating any supposed benefit of the sick person not just staying home in the first place), and at worst it's spreading a flu that eventually results in someone dying.

On top of that, a massive number of companies have just proven remote work is possible, even during entirely non-ideal conditions (lockdowns, virtual school, high stress, etc).

One time I was really sick at an airport McDonalds. Fever, sneezing, the whole thing. But you're in an airport, and you have to eat something.

I had to explain almost pedantically why they should allow me to order verbally instead of using their touchscreens, for the safety of the other customers.

I think today, they'd have a protocol to accommodate people who are obviously sick so they don't have to touch anything. In fact, they probably don't even let healthy people use touch screens, if I had to guess.

You didn’t think of just washing your hands and maybe using a knuckle to touch the screen instead of going HN pedant on the $7/hr worker?

Besides, I would think shooting mucus debris in their direction by talking is worse than using a cleaned knuckle on a screen far away from them.

So, in your expert medical opinion, given years after the fact without any understanding of the illness in question... You think that your advice that "you should just have washed your hands" is such amazing advice that you think it's worth writing here?

What are you hoping to gain? And even if you were right, as I said, I had a high fever. It's not like I was thinking clearly. Are you trying to feel morally superior to someone who was in gravely ill?

Every fall, winter and spring, I was able to watch as colds and the flu spread around indoors. People would be chastised for staying home with "the sniffles", too.

But the flu has always been here, even when our country was significantly less populated, when we were significantly more rural, and when people were significantly less connected in many ways. Like, how did we get flu pandemics in the 1700s? Weren't we less connected back then, even after you account for all the social distancing that was done this year?

The flu (influenza) has been linked to solar radiation and electricity.

-- quote --

In 2001, Canadian astronomer Ken Tapping showed that the influenza pandemics over the previous three centuries correlated with peaks in solar magnetic activity, on an 11- year cycle. It has also been found that some outbreaks of influenza spread over enormous areas in just a few days – a fact that is difficult to explain by contagion from one person to another. Also, numerous experiments seeking to prove direct contagion through close contact, droplets of mucus or other processes have proved fruitless.

From 1933 to the present day, virologists have been unable to present any experimental study proving that influenza spreads through normal contact between people. All attempts to do so have met with failure.

-- end quote --

source: https://www.5gexposed.com/wp-content/uploads/2019/04/English...

5gexposed.com is not really a reputable source. Anyway,

> Also, numerous experiments seeking to prove direct contagion through close contact, droplets of mucus or other processes have proved fruitless.

> From 1933 to the present day, virologists have been unable to present any experimental study proving that influenza spreads through normal contact between people. All attempts to do so have met with failure.

This is just demonstrably false. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3682679/

I mean maybe there are viral aerosol reservoirs in the clouds but posting stuff from a website called 5gexposed is not helping your case.

> Like, how did we get flu pandemics in the 1700s?

Germ theory of disease didn't exist back then.

Some of those "flu" pandemics may not have been caused by influenza viruses.

I'm really hoping that the culture change in the US is to wear masks in public when feeling ill from a respiratory infection.

Not wearing masks is a hill many people have chosen to literally die on, so while I hope that there is a culture change, I expect that anyone wearing masks after the pandemic is over will be demonized.

I'm really hoping that the culture change in the US is to wear masks in public to thwart facial recognition.

Better yet just stay home.

Also, I wonder if there is correlation of at-risk people getting more flu shots?

Not sure what the case is overall, but apparently in North Dakota, where flu cases were 1/65 of what they were the year prior, flu vaccinations are only up 5%: https://kfgo.com/2021/04/29/319613/

> The likely explanation is that, because the flu is significantly less transmissible than COVID

But why is it less transmissible? One obvious explanation is because we've lived with it all our lives, and most people already have some level of pre-existing immunity to most flu strains they're exposed to. Both due to natural infections, and vaccines.

> In other words, you can probably beat back the flu significantly by having enough of the population mask up, wash/sanitize their hands, etc.

If pre-existing immunity is why it's less transmissible, those measures will result in fewer flu infections, and thus lower levels of pre-existing immunity. Which in turn, may make the flu more transmissible, leaving us where we started. Worse, if pre-existing immunity is decreasing the severity of the infections we do get, the net effect may actually be more deaths due to fewer, but more deadly, infections.

Flu vaccines are notoriously ineffective, with a typical year being just 50% effective, and bad years being as little as 19%. They're probably the least effective widely used vaccines by a long shot (eg the MMR vaccine is about 97% effective). So we can't just assume we'd be able to make up the difference with increased vaccination. Flu vaccine coverage is already quite high anyway, 51.8% or so for the entire US population.

edit: fixed %

https://www.cdc.gov/flu/fluvaxview/coverage-1920estimates.ht... https://www.cdc.gov/vaccines/vpd/measles/index.html https://www.cdc.gov/flu/vaccines-work/effectiveness-studies....

Transmissibility (or Basic Reproduction Number - R0) is an intrinsic characteristic of a disease.

Measles is at least 3 times more transmissible than flu [1].

We have a very effective vaccine against measles and a mildly effective one against flu, so people get flu and not measles but let them circulate among people without any protection and measles will get them sooner than flu. And it's also much deadlier [2]

[1] https://transportgeography.org/contents/applications/transpo...

[2] https://academic.oup.com/jid/article/189/Supplement_1/S4/823...

> Transmissibility (or Basic Reproduction Number - R0) is an intrinsic characteristic of a disease.

I'm not talking about the theoretical R0, which assumes an immunologically naive population. I'm talking about the real world reproductive ratio, R, including existing immunity. Estimates of real world R for influenza are are even lower than the 2-4 your source quoted. Eg, this paper estimates a median of just 1.3 for a typical year's seasonal influenza: https://bmcinfectdis.biomedcentral.com/articles/10.1186/1471...

With COVID-19's R0 estimated at 2-3, it could easily be the case that our measures are sufficient to completely wipe out the flu. But not COVID-19: https://www.thelancet.com/journals/laninf/article/PIIS1473-3...

Re: measles, note that pre-vaccine, almost everyone got infected with measles at some point in their life, usually as a child. You actually see this in how effective the early childhood measles vaccination programs were: even though only children were being vaccinated, a small % of the total population, measles rates dropped dramatically(1) almost immediately. The adults had already gotten it and were already immune. So to wipe it out, we just needed to protect those who hadn't been infected: the new, uninfected, children born every year. The measles vaccine is attenuated live measles after all. So by vaccinating, we just get the inevitable infection over with in a controlled way, with the odds rigged _enormously_ in your favor.

1) https://ftp.historyofvaccines.org/index.php/content/graph-us...

> With COVID-19's R0 estimated at 2-3

I haven't been keeping up with it, but that's the lowest estimate I've seen yet. Back when it was still only known to be in China it was estimated at 5-6, but quickly went down to 3-4 for the first several months or so of last year, then some estimates brought it back up to 5-6..

Your link says that flu shot coverage is 51.8% for all people over 6 months of age. The 64% number is for children.

Flu vaccine effectiveness is not great because they have to "guess" which variants of the flu will be most prevalent months ahead of time due to the manufacturing lead times. A lot of experts are optimistic than the mRNA vaccine technology will lead to more effective flu shots.

Thanks! Fixed.

> A lot of experts are optimistic than the mRNA vaccine technology will lead to more effective flu shots.

We will see. Influenza is unusual in its ability to evolve new variants that resist existing antibodies. It's also not clear that we even can give people repeated mRNA vaccine shots year after year. People quite often develop antibodies to glycol, which makes up the nanospheres used to get the mRNA into cells. Repeated shots may lead to severe side effects, and/or the nanospheres being destroyed before the mRNA can be delivered, rendering the vaccines ineffective.

Incidentally, this is also a problem with the new adenovirus technology used in the Astra Zeneca and Johnson & Johnson vaccines: your immune system develops antibodies to the carrier virus as well as the target proteins. Subsequent shots with the same adenovirus can be destroyed prior to being able to get into cells and express the desired protein; there isn't an infinite supply of suitable adenovirus strains. The Sputnik V vaccine actually uses a different adenovirus for the first and second shots for this reason.

I think this was only a problem with the HIV adenovirus vaccines.

> But why is it less transmissible? One obvious explanation is because we've lived with it all our lives

Haven't we lived with different types of coronaviruses all of our lives as well, though? It seems at least equally as plausible that COVID is more transmissible due to actual physical qualities of the virus with respect to replication rate, particle size, and other factors that cause more virus to be expelled from the body in different ways. It could be that the flu is more transmissible by fomites than through aerosols, or that less flu virus tends to be expelled by the body, or that the flu virus has a more difficult time in infecting our cells compared to SARS-CoV2.

Of course, this is pure speculation on my part, but from what I can tell we lack data for anyone to be drawing any firm conclusions on this point.

That's not at all an obvious explanation.

There obvious explanation is that different diseases have different levels of infectiousness. It just so happens that the symptoms the flu causes make it less virulent than covid-19.

Large indoor gatherings, indoor restaurants, bars, were shut down for months. Grocery stores enforced or at least encouraged their own mask policies. What’s more in Florida, those few steps covered almost all the ways people really interact there. Like much of the US, there is almost zero spontaneous sharing of space outside of bars, restaurants, stores and churches.

I personally dislike the isolation of extreme car culture, but it does help in situations like this.

I never really thought about how America's aversion to public transit could be a positive in a pandemic. Interesting point.

I was in Florida two weeks ago--Orlando and Sarasota. I'm a Massachusetts resident. In Florida, I observed around 90+% mask usage in grocery stores. In a random ColdStone creamery, I saw maybe 70%, Five guys was probably 80% except while eating.

In Massachusetts, usage is certainly higher, but maybe in practicality, not enough to make a difference compared to other factors?

1% mask usage in Sweden and we also have extremely low flu numbers.

Interesting. Do people still associate indoors in large numbers, or is that unchanged as well? As in, could behavioral change be a driver?

I also wonder, with far less numerical opportunity to spread and mutate, if the flu wasn't able to "grow" a good candidate with good evolutionary fitness this year, so distancing and mask usage affect countries even where they aren't practiced.

No, we have other restrictions and recommendations resulting in various degrees of social distancing. Definitely less than countries that did lockdowns but it's probably as you say a combination of our own measures and other countries' more rigid restrictions (including masks) killing off the international transmission routes. So we should be thankful that other countries took this more seriously if that's the case.

>Why did the flu also disappear in the states that had effectively no covid restrictions?

Where are you getting this take? Life in the US in 2020 is dramatically different than it was in 2019.

> states that had effectively no covid restrictions?

This isn't really true anywhere, some places had fewer state mandated restrictions, but effectively everywhere had significant changes in terms of breadth and depth of person-to-person contacts.

You seem to be implying that Florida had no restrictions, but this just isn't the case. Even when I went a couple of months ago, masking indoors was the norm and most places still had capacity restrictions.

Queues at popular sites were socially distanced outdoors as well.

A single data point: I didn't get flu once since I went self employed and started working from home most of the time in 2006. Less public transport, less open space offices, less restaurants at lunch time. Maybe a coincidence but if people had less chances to meet other people, maybe because those other people kept social distancing, then they had less chances to get flu. It's way less contagious than covid to start with.

Behavioral change. Flu is generally less infectious than covid, so it will take less voluntary behavioral change to get the flu R-number below 1 than the covid one.

Also, the whole hand-sanitiser-everywhere thing, while in retrospect probably not super effective against covid, would be expected to be quite effective for the flu.

1. All places had COVID responses, even places that didn't have state-wide rules. I doubt that there were any real number of Americans -- even in isolated communities -- whose lives were not impacted by public health stuff during COVID.

2. Having flu outside your border be rarer means less flu coming in.

There are a bunch of contributing factors (most schools, indoor public places, and workplaces encouraging or requiring masks, and many workplaces remote), but one thing that I'd expect to help with flu much more than it does with COVID-19 is sick people staying home.

Asymptomatic spread is a much larger risk with COVID-19 compared to the flu. A simple behavior change of "If I feel sick, I don't go to work/school/grocery shopping" isn't enough to stop COVID, but could cut flu spread a ton by itself.

It's pretty huge that people with cold/flu symptoms now stay home or mask up. People used to just cough and sneeze everywhere.

Short answer is that photos of people on the beach are an incomplete representation of the situation in Florida.

Flu disappeared globally. With no incoming cases, it would have had to spread simply by internal transmission, which by definition would be less than usual.

Also, there were probably minor restrictions people took upon themselves, like staying home when they had flu-like symptoms, or shunning people that coughed.

Flu is seasonal, and there are large pushes to get people vaccinated against flu each year. Sometimes those vaccinations are more effective, and sometimes you get more people vaccinated. This season it appears both are true.

It's only seasonal because of increased indoor/outdoor humidity permitting longer micro-droplet aerosol suspension. If everyone were wearing masks that trap micro-droplets, then flus and colds effectively die out. It's the no maskers and chin-guarders that cause infectious agents like SARS-CoV-2, flu, and colds to proliferate.

The notion that horizontal interdiction is responsible for this suppression is absolutely, positively absurd and will never stand up to scrutiny.

On the other hand, this patterns very neatly with previously observed and well-documented phenomena of viral interference, specifically with respect to influenza. Here's a good paper to start a journey of research on this topic: https://academic.oup.com/jid/article/212/11/1690/2911897

Norovirus was also decimated last year, and it doesn't infect the same organs/cells as respiratory viruses: https://www.cdc.gov/norovirus/reporting/norostat/data.html

Sure. I think it's plausible that widespread surface sterilization is responsible for suppression of fomite transmission.

Apart from what others said. Flu is seasonal and (most of the time?) starts in Asia. With very restricted international travel flu simply has less possibilities to come over.