the ‘Spanish’ flu

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It was terrible, killing millions.

Where has it gone? Is it still around?

In: Biology
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It was a worse vivid from prob the Us, which the Yanks brought to the western Front in WW1. The News were censored BC of the war, but not in Spain, so it seemed like it came from there. Most people died BC of fluid building up in the lungs, drowning them in their own fluids. There were 3 Waves, of which the 2. was the most deadly. There were no ventilators, so the most patients died BC of that. It is still around as far as I know.

Well i can tell you that it was called the “Spanish” flu because only the Spanish (Spain) media was reporting on it. Everyone else had a media blackout because it was bad for war moral to report it. The gov wanted to play it down like some tried to do with covid. Like many plagues it mostly ran it’s course. A virus that’s so deadly so fast can’t really survive if it kills everyone.

They are not sure where it started, but the two most likely places are the US and China based on outbreak patterns. The reason it is called the Spanish Flu is that Spain was basically the only country that reported on it as the others were in media blackout during the war. The theorists that think it originated in China think that it was related to the flu strain that came in the 1880s which is why older people seem to have survived it better as they had partial immunity.

As for why it was so terrible. That is due to WWI. The armies living in dirty fetid conditions in cramp quarters means disease spreads quickly and troop movements across continents means it spread far.

As for where it went? It is still among us. It has become a part of the seasonal flu once a large enough percentage of the population survived it and gained immunity or partial immunity.

Most of the people either died or became resistant to the version of the flu, with no carriers able to transmit the strain H1N1 so it mutated into swine flu and other variants. https://youtu.be/Qh03tYOqmdo

We did not have the reasearch tools at the time to track the lineage of the virus. We did not even properly know about viruses at that time. And virus samples do not last long. But we are pretty certain that it was a variant of the H1N1 and closely related to the 2009 swine flu pandemic. It may in fact be one of the first variants of this virus to infect humans which might explain its deadlieness. There are lots of variants of the H1N1 virus infecting both humans and pigs and potentially other animals as well. We do not know which developed from the 1917 influenza specifically or even if all of them did. Most of these only give mild symptoms which is why they have been able to stick around as long and is one of the viruses that give seasonal influenza. However other variants can be quite deadly but this also means that they tend to be controlled rather quickly, if not by the authorities then by the sick themselves staying home and isolating.

It’s become endemic, meaning it circulates through the population and pops up especially during winter. It has also mutated to become less dangerous.

This is the typical process for viruses that jump from animals to humans. Initially, the virus is more dangerous. See, viruses mostly evolve to keep their target hosts alive. If a virus is very deadly then it doesn’t spread well. So deadly viruses die out while less-deadly ones stick around and multiply. But when a virus jumps to a different host, e.g. to humans, all bets are off. The virus hasn’t adapted to thrive in that host and so it may end up being more deadly.

Next, one of two things happens. Either the virus doesn’t fare well in humans (because it’s just too deadly or doesn’t spread easily) and dies out, or it sticks with us. In the latter case, it has the potential to cause a pandemic, because it’s a new virus that no one in the world has any immunity to. This is what happened with the Spanish flu a century ago, and what happened with SARS-CoV-2 recently.

Because no one has any immunity, the virus can initially afford to be a little “sloppy” as far as adaptation to humans is concerned. It can afford to be a little more deadly than your typical ‘flu or cold, for instance. Over time, though, people will build up immunity to the new virus. At the same time, the large reservoir of infected people will lead to new mutations popping up. The selection pressure on these mutations will favor those that make the virus spread more among humans. This can include adaptations that just help the virus enter our cells, for instance, but also adaptations that make the virus less severe, because a less sick person is more likely to transmit the virus to others* (esp. compared to a dead person). As more and more people become immune, an additional selection pressure starts to build towards simply changing the virus to become less recognizable to immune systems that have already faced it before.

(*Edit: just wanted to clarify that some symptoms of course make the virus spread more, such as coughing or sneezing. But those aren’t *serious* symptoms (normally). What you want to avoid, as a virus, is making people so ill that they don’t leave the house and reduce their contact with others. Ideally you want people walking around pretty happily whilst simultaneously coughing, sneezing, blowing their noses, etc.)

So, generally speaking, the process of a virus becoming endemic is accompanied by that virus becoming less dangerous to us. This is also what is likely to happen to SARS-CoV-2. It is true that people are predicting that we will be needing booster shots of the vaccine for a while, but that doesn’t mean we’ll need those forever – at least not the whole population. In a sense, we are also still giving people yearly shots for the “descendants” of the Spanish Flu virus – just not everybody but only those who are at risk of death or serious illness if they get infected. This is a likely outcome for SARS-CoV-2 too. But there may be an intermediate period where the level of immunity among the population, as well as the seriousness of the current virus strain makes it a good idea to keep vaccinating a large part of the population, until we’re sure that the virus has reached a level where this is no longer necessary.

(Disclaimer: the above is what I understand to be the likely outcome given an informed layperson’s understanding of immunology and epidemiology. It is not an expert’s opinion, and even if it were I don’t think an expert would be certain either. But this (AFAIK) is what has always happened with new viruses so far, and so it seems plausible that something similar will happen this time.)