For help, advice and discussion about stuff not related to aviation. Play nice: no religion, no politics and no axe grinding please.
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By Sir Morley Steven
FLYER Club Member  FLYER Club Member
#1886818
A virus that kills or hospitalises its host becomes less infectious due coming into contact with fewer people. Its personal R rate will therefore be low.
A virus that gives you mild or no symptoms is more infectious (or has a greater R rate of its own) due coming into contact with more people.
Thus, variants of the latter type will be less serious?
In time viruses will, by this logic, become less dangerous.
Is that flawed logic?
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By Flyin'Dutch'
FLYER Club Member  FLYER Club Member
#1886821
Sir Morley Steven wrote:A virus that kills or hospitalises its host becomes less infectious due coming into contact with fewer people. Its personal R rate will therefore be low.
A virus that gives you mild or no symptoms is more infectious (or has a greater R rate of its own) due coming into contact with more people.
Thus, variants of the latter type will be less serious?
In time viruses will, by this logic, become less dangerous.
Is that flawed logic?


You can't generalise like that as there are too many other variables.

A virus that instantaneously kills the host will ultimately kill fewer.

A more infectious virus that kills fewer over a longer period of time will ultimately kill more people.
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By lobstaboy
#1886824
(Not a doctor but I do have access to relevant epidemiological expertise)
The death or otherwise of the host animal is of no 'interest' to the virus as long as it gets time to infect more than one other host.
So another key factor is how long the host is infectious before it becomes illl enough to change it's behaviour (which could include dying).
Apparently other animals also modify their behaviour when ill in ways that reduce infection rates (maybe obvious but I only learnt that recently)
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By PeteSpencer
FLYER Club Member  FLYER Club Member
#1886826
Certain viruses strengthen in virulence as they pass through a close knit community.

So if a virus brought home by kids from school, for example , flashes through a typically huge sometimes ethnic extended family in the Midlands living in close quarters , something that causes a mild snuffle in a five year old can easily finish off granny .

The phenomenon is known as ‘ viral passage’ pronounced the French way like ‘massage’.
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By leiafee
FLYER Club Member  FLYER Club Member
#1886832
Sir Morley Steven wrote:Is that flawed logic?


Not any kind of expert but the fact we still have lots of very deadly disease that haven’t evolved themselves to harmlessness suggests it must be…

Plenty of death available in the gap between “absolutely most evolutionary efficient” and “adequate number survive long enough to reproduce”
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By TopCat
FLYER Club Member  FLYER Club Member
#1886833
Sir Morley Steven wrote:A virus that kills or hospitalises its host becomes less infectious due coming into contact with fewer people. Its personal R rate will therefore be low.
A virus that gives you mild or no symptoms is more infectious (or has a greater R rate of its own) due coming into contact with more people.
Thus, variants of the latter type will be less serious?
In time viruses will, by this logic, become less dangerous.
Is that flawed logic?

Yes, it is flawed logic.

It is true that a virus that has a short incubation period, and causes symptoms so bad that its victims can't get around will have a low R value. This (and the fact it's not airborne) is why Ebola outbreaks tend to die out.

It's also true that a mild virus can have a large R value because its vectors are out and about spreading it. The common cold, for instance.

However, there is no causal relationship between the two. This is because the mutations that give rise to new variants are random. There is no 'guiding force' behind such mutations with any kind of objective. If it so happens that a new variant is more transmissible than another, it will propagate more effectively. This is what happened with Delta, and is probably now happening with Omicron.

Whether new variants result in different symptoms is completely separate, and as others have said, if the host dies it's of no evolutionary significance if the virus has already infected other hosts in the meantime.

Smallpox was around for 3000 years without getting milder. HIV is still lethal without the anti-retroviral drugs that can treat it. Flu is sometimes mild, and sometimes not.

We absolutely cannot rely on Covid becoming milder. Even if it did, there's no reason yet another variant wouldn't arise that was more serious again. The original SARS was a lot more lethal than the current one, and MERS was a lot more lethal still. We were just lucky that they weren't very transmissible.
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By Sir Morley Steven
FLYER Club Member  FLYER Club Member
#1886838
Didn’t know you were a doctor Top cat.
You appear to have the medical opinion that my logic is flawed yet you simply repeat my own.
Still, you are a doctor so I must be wrong.
By TopCat
FLYER Club Member  FLYER Club Member
#1886841
Sir Morley Steven wrote:Didn’t know you were a doctor Top cat.
You appear to have the medical opinion that my logic is flawed yet you simply repeat my own.
Still, you are a doctor so I must be wrong.

Eh?

What makes you think I'm a doctor, or that only doctors know anything about virology, evolutionary biology, epidemiology, or genetics?

Or logic, for that matter. Your mistake was in assuming that your conclusion followed from your premises. It doesn't.

Your logic is quite suspect, I have to say - it also doesn't follow that if I was a doctor, you must be wrong. Again, there's no causal relationship between the two, either way. The fact that you're wrong isn't because I'm not a doctor :)
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By Sir Morley Steven
FLYER Club Member  FLYER Club Member
#1886842
There’s a clue in the title.
Your opinion that my logic is flawed is as meaningful as my logic itself if it is not based upon evidence.

Unless you are an epidemiologist? You one of those?

Anyway I have seen nothing to show that a less deadly virus will replicate at the same speed as a deadly one.

The point about old deadly viruses might be valid but I am guessing that stuff like smallpox etc either mutate differently or not at all? How did the vaccines work for such a long time?
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By lobstaboy
#1886851
I'll answer the implicit question that dare not speak it's name that's behind most enquiries like Sir Morley's
Is it theoretically possible for a virus to wipe out enough people that civilization collapses, and we end up in a zombie movie-like situation?
Yes it is.
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By Cessna571
#1886884
I am not a doctor, but I am helping write some software that is helping crack this.

I work with people who understand it more than any GP will, though I’m a “Computer Programmer” not a Bio Scientist, we do discuss things sometimes.

Remember it’s a virus, it has no grand plan to be successful, it’s not even alive.
It’s not evolving.

If it mutates to a state that simply wipes everyone out, that’s what will happen.

I find it really hard to get my head round that it may just wipe out all it’s hosts.

The whole thing is a chaotic game of chance, a statistical exercise, where the virus mutates and we evolve.

It mutates quickly, we evolve slowly, but we have lots of defences floating around in our bloodstreams built up over eons that mean unless we are really unlucky it won’t get us all.

Those it doesn’t get, procreate and round we go again.

I’ve had conversations with people that really understand it, and tbh it’s beyond my ken, it’s fascinating though.

The ones I’ve spoken to don’t think it’ll get us ALL because of the way we work. So that’s slightly reassuring on a species level.

I don’t remember there being any correlation between deadliness and R number, they’re different things, of course it can be highly infectious and highly fatal, why not?

Imagine how frustrated some of these people are, that they understand it, and it’s not something you can explain quickly, or even that everyone can comprehend, and because of that people prefer to believe some of the guff on the internet.

Also of interest is that the real explanations are on the internet, but who is reading pubmed or medrxiv preprint down the pub?! Who can comprehend it anyway?!
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By Bill McCarthy
#1886914
Yet again, people have not learned the lessons of history. In my childhood days, inoculation against all manner of diseases - diphtheria, smallpox, polio etc where looked upon as miracles of science. Millions of lives have been saved since the development of penicillin, yet we take it for granted and demand it’s prescription.
The population back then didn’t doubt the power of their effect.
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By kanga
#1886915
Just to cheer you all up, Prof Gilbert's Dimpleby Lecture is being broadcast tonight, and has already generated some headlines (and predictable online Comments)

https://www.bbc.co.uk/news/health-59542211

The 44th Richard Dimbleby Lecture will be broadcast on BBC One and iPlayer on Monday 6 December at 22:35 GMT.


"Sarah Gilbert: Next pandemic could be more lethal than Covid"
By johnm
FLYER Club Member  FLYER Club Member
#1886922
Professor's Gilbert's message is basically " learn the lessons. be prepared and make sure the "miracle" vaccine development timescales become the norm", all of which implies some serious science funding.....
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