> Most virus infections can cause long term problems.
This is very, very false. Your body is currently fighting off a very large number of virus and bacterial infections. Most are innocuous, and don't even raise the symptoms of a cold.
Now, going out on more of a limb and moving into speculation:
There is a tiny minority of diseases -- most very new and poorly-understood -- which do this.
There's some evidence that prior to around 10,000 BC -- the rise of civilization -- very few diseases like this existed. What appears to have changed was that with civilization -- and now with population density and travel -- diseases can co-evolve with humans, and integrate into our various chemical signalling pathways. Things like Covid or AIDS can explicitly target our immune system, for example, to try to avoid being caught.
* Prior to civilization, a successful disease had to work across a broad range of species.
* When the population was a fraction of what it is today, there was less opportunity for disease to evolve.
* Without travel, there was less opportunity for spread (and for crosstalk between viruses)
... and so on.
These relatively new diseases can cause long-term problems. There's a lot of them, and it's not always the same ones as cause acute symptoms!
Fundamentally, prior to civilization there was not a sustainable host population for human diseases. Anything that could only target humans would quickly burn out as everyone around would either be dead or resistant from prior infection.
As our population grew and contact grew there were enough people around that a disease could sweep through a population then go elsewhere while a new generation grew up to be vulnerable when it finally came back.
Even with that, though, most of our disease are minor variants on stuff from the animal world. Covid appears to be simply the latest iteration of something that has periodically spilled into the human population in the past--except with the extremely nasty trait of asymptomatic spread. HIV is simply a minor variant on the already-existing SIV. It learned to target the immune system long before it targeted humans.
Herpes virus at least has been infecting humans since long before the rise of civilization. Once a person is infected they can remain a contagious carrier for life, so there's plenty of opportunity to spread it even with lower population density.
This is very, very false. Your body is currently fighting off a very large number of virus and bacterial infections. Most are innocuous, and don't even raise the symptoms of a cold.
Now, going out on more of a limb and moving into speculation:
There is a tiny minority of diseases -- most very new and poorly-understood -- which do this.
There's some evidence that prior to around 10,000 BC -- the rise of civilization -- very few diseases like this existed. What appears to have changed was that with civilization -- and now with population density and travel -- diseases can co-evolve with humans, and integrate into our various chemical signalling pathways. Things like Covid or AIDS can explicitly target our immune system, for example, to try to avoid being caught.
* Prior to civilization, a successful disease had to work across a broad range of species.
* When the population was a fraction of what it is today, there was less opportunity for disease to evolve.
* Without travel, there was less opportunity for spread (and for crosstalk between viruses)
... and so on.
These relatively new diseases can cause long-term problems. There's a lot of them, and it's not always the same ones as cause acute symptoms!