[Closed] Viruses - what happens to variants?

I actually don't want to discuss just Covid-19 here, it was something I'd wondered about more generally to do with viruses. The yearly strain targeting flu vaccines got me thinking about it. E.g. where do the other flu strains go that year? Are they extinct?

Also "you never catch the same cold twice" apparently. Is that immunity or because old strains cease to exist, or both?

Might be difficult to avoid straying into Covid-19, but hopefully we can keep it generalised (and the mods happy). There are some knowledgeable people on here who it would be great to hear from

Generally they are outcompeted but the new strains and they die away. It’s just a form of evolution/natural selection, in which the selective pressure is largely the ability to avoid the immune system of the virus’s host. Old strain get hammered by the immune system, the new one escapes for a while until immune system catches up, and a new strain emerges…repeat. The new strain doesn’t do anything to the old strain, it’s just ‘better’. You can be infected by two strains, so someone could have two strains of flu or covid or whatever.

Also “you never catch the same cold twice” apparently.

I would go for thats unproven/it depends on how quickly you shake it off. Next year then yes your immune system is probably prepped for it but beyond that whilst it might be programmed for it still could take a bit more time to kick in.
My understanding is that it isnt so much one blocks another as opposed to it gets to your first.
Once you get hit by something the immune system starts to respond. If it is something similar enough to what it has seen before then the immune system can respond faster and hence probably wipe it out before you notice it. Bit like daily hate readers waiting for a mention of cyclists jumping red lights. They will be ready and waiting but if we said unicyclists it might take a bit longer to get them frothing.
So for the viruses (viri?) if you get infected by variant x first then you may spread it to others before your immune system responds and kills it off (hopefully). If you get hit by variant y a week later then if it is close enough to x your immune system will kick in and kill it off before you infect anyone else. So overtime the one which spreads fastest finds a vulnerable host before the less fast spreading strain.

Flu is a good example. The vaccine is actually vaccines since for those of us in the UK what happens is midsummer the scientists look at the most current variants in asia and try to produce vaccines for the top 5 or so variants to put into the "vaccine". If they get it right then the vaccine is relatively effective but if it is wrong then it drops massively.

Bit like daily hate readers waiting for a mention of cyclists jumping red lights. They will be ready and waiting but if we said unicyclists it might take a bit longer to get them frothing.

Love this analogy! 😄

Also “you never catch the same cold twice” apparently. Is that immunity or because old strains cease to exist, or both?

What we think of as a 'cold' is the symptoms not the virus. The symptoms aren't the virus's creation they're ours - they're  you're immune system's way of dealing with a whole panoply of different infections. The sore throat, snot, temperature, and so on, thats not the bug doing that, its your immune system attacking the bug. The viruses hijack cells and use them to reproduce - which for you doesnt fell like anything - this is the period when you are asymptomatic and infectious.- your immune system recognises that hijacking and attacks those infected cells - that feels rotten - thats when you feel ill - attacking the viruses creates a lot of collateral damage -  thats the sensations we feel and they are all your own doing.

The severe and fatal instances of Covid we are seeing is those people's immune systems spiralling out of control.

There are somewhere in the region of 200 conditions that we call 'a cold' so the bug you get one year isn't necessary a 'strain' of one you got last year as there are whole classes of different viruses all with different and new strains emerging and  circulating - coronaviruses, rhinoviruses, adenoviruses, enteroviruses and so on - all entirely different, all feel the same in terms of how our body reacts to them.

We typically get 2-3 colds a year, but with 200 out there to catch its unlikely your next cold is an evolution of the last one you had but its likely you'll encounter several variants of a virus in a lifetime.

We're thinking about this in quite distorted terms at the moment because the novel strain of coronavirus is so incredibly infectious, its operating well outside the norms of all the other bugs we encounter.

We’re thinking about this in quite distorted terms at the moment because the novel strain of coronavirus is so incredibly infectious, its operating well outside the norms of all the other bugs we encounter.

Nothing compared to measles though.

Smallpox has an R0 of 3
Polio has an R0 of 4-6
Mumps has an R0 of 10-12
Chickenpox has an R0 of 10-12
Pertussis has an R0 of 15-17
Measles has an R0 of 16-18

Nothing compared to measles though.

Indeed but there aren't lots of conditions with symptoms like measles to confuse measles with though. What I meant was of all the 'Common Cold' like viruses we can get we never really know what one we have but within that spectrum of conditions SARS Covid is especially infectious. We're able to distinguish it not by symptoms (which for most people is quite a mild condition)  but by testing, monitoring and reporting. You'd know if you got SARS Covid twice or never because we test for it (I've been tested 2-3 times a week for the last 14 months so I'm as confident as anyone can be that I've never had it). I don't know if I've had any version of Rhinovirus once, twice, a hundred times because its not something that is routinely identified to individuals by testing -  but I've had stuff that feels like it a lot. What kinds of 'common cold' I've had or not had I'll never know.

Polio has an R0 of 4-6

Interesting how short our memory is about Polio - I remember parents at the school gate growing up who were victims - luckily only reasonably lightly effected in terms of fairly modest deformity and disability. It seems to be strange that a pandemic only one generation away isn't on our minds at this time

Happened across this item reminding us that there are still people in Iron Lungs from that outbreak

So for the viruses (viri?)

"Viruses" is correct English. "Virus" comes from Latin so if it had a Latin plural then I believe that would be "vira." I'm not wholly sure why we don't use the Latin form, maybe it just never came up back in the day?

“Viruses” is correct English. “Virus” comes from Latin so if it had a Latin plural then I believe that would be “vira.”

agreed - except it would be "viri"

scientists look at the most current variants in asia and try to produce vaccines for the top 5 or so variants

Why does Flu circulate in Asia first? Or is it because it's a much larger sample set, so it reveals trends that, at the time, are not traceable in the west? These won't become significant in the west until everyone goes indoors for winter and more people get flu?

A bit of thinking out loud, a strain of a virus is happily hopping host to host, but then a faster more virulent strain emerges. Why does that new strain stop the other strain hopping host to host? Is it because the former strain's next potential host is now off work, ill in bed with the new strain? The transmission vector is no longer there as they aren't in the office anymore. I.e. it's the behaviour that one strain instigates in a host that stops the other strain spreading.

I think just writing that out helped me understand it. It's why lockdowns work.

Also “you never catch the same cold twice” apparently.

We do, but not always from rhinovirus (HCoVs also give colds). New strains outcompete and old strains die away - or head to another reservoir. Influenza likes birds in Asia.

The competitive advantage can be "more spreadable", but it could be "more people to infect". That's omicron people can be reinfected by omicron but not immediately by delta because the population has some immunity to delta (some of which is from vaccines). influenza is the same, the two surface proteins change, probably due to animal selection pressure, then head into humans. In Asia there may be closer proximity to animals, hence the initiation.

I’m no scientist, virologist or whatever, but I do have a layman’s interest in a whole range of things, and I’ve been reading a lot of news items about SARS-Covid, and it’s history and how it’s likely to change and mutate, and there’s a number of things that have got my attention recently. A while back, a number of comments were made suggesting that, over time the current Covid outbreak could become little more than a regular nuisance like the ‘common cold’, itself a coronavirus, has become. Then the latest Omicron variant appeared and a detailed genetic breakdown showed that it had picked up bits of genetic material from both HIV, unsurprisingly considering it originated in South Africa, but also the common cold, or one of its variants. Now Omicron is spreading like wildfire, but it doesn’t seem to be causing as many hospitalisations or such serious illness as Delta, which does kind of suggest that, while it’s certainly more contagious, it may be losing its strength, which has caused at least a couple of people in the field to suggest that these might be indicative of the virus doing exactly that, becoming just another, admittedly unpleasant thing to deal with, but not a mass killer.

Fortunately, we now have some extraordinary people who’ve developed some equally extraordinary science in virology which is proving far more effective than anything we’ve ever had before, and which can only become more effective as time goes on.

Leaving aside, of course, really stupid people who refuse to entertain the notion that a simple vaccination will not only help protect them from a serious illness and possibly death, but also those close to them. And for which I have no reasonable answer.

I watched this the other day, was quite interesting.

What CountZero said tallies with a virologist speaking on the radio the other day. Essentially he said that the original and more dangerous covid virus was mutating into a weaker but more transmissible variant, omicron. Regularly seen behaviour in other viruses apparently.
He saw it as a good sign although in a more measured way than I've spelt it out.
It put a smile on my face listening to what he had to say.