timppu: Yeah we had Black Death... Anyway, to a commoner like me it would appear that by default evolution does not favour microbes which are lethal because if they kill their hosts (fast), they are also rather short-lived. I would think nature prefers micro-organisms which spread easily, but are harmless to its host.
But I guess these are special cases where some harmless micro-organism becomes lethal by accident, or intentionally by a nutjob. But the point is that it is against the microbe's own survival and "agenda" to be lethal to its hosts (I assume; I am not a biologist).
It is true that in evolutionary biology we used to think this way, but since then we've modified the position somewhat. The reality of the situation is that by virtue of a pathogen's mechanism of spreading there is a certain amount of damage it has to do and it is not necessary that the damage be completely nullified even when in the pathogen's "best interest". Remember, pathogens have no predictive power, they can only respond to pressures that are currently exerted and act on mutations that are actually capable of occurring. It is true that a pathogen's mortality rate does tend to drop when it adapts to be communicable between members of its new host species for the reasons you mention. Sadly there are few instances where a pathogen becomes commensal or even symbiotic though as despite it being in the organism's "best interest", it often simply isn't possible.
timppu: Anyway, I try to ease myself with "we all die sometime anyway", and "so and so many people die every year of cancer, heart failure, traffic etc. anyway", ie. in the cosmic scale it doesn't really matter even if half of the population died quickly. Sure there would be lots of grieving, but then that's just the human nature. We are still here after Black Death, and even if we weren't, so what? As long as the penguins survive.
Shloulet: I don't buy into the influenza is going to wipe us all out claptrap. The so-called "Spanish flu" outbreak killed ten percent of infected persons or less, against a back-drop of total war. That means rationing of everything from a to z. That means poorer diets and weakened immune systems for the entire population. The only think keeping people more scared of influenza than HIV/AIDS is right-wing Christian propaganda. So long as we can convince people that anything other than a respiratory illness is punishment from God or the soviet union or whatever, we can exploit influenza as a means of installing stricter and more authoritarian disaster management techniques in the face of an epidemic that happens two or more times a year. Giving people the choice of wearing a condom? Morally questionable. Shutting down travel and scientific inquiries? Morally right and totally necessary.
The trouble with it it is the time scales on which people die over (and here I am going to address two points one from you and one from Shloulet) - which is why Shloulet doesn't understand the real difference between the panic over the Flu versus AIDS. It has nothing to do with conspiracy theories either about AIDS (which he complains about) or about the Flu (which he seems to propagate - I hope I misinterpreted the above) and everything to do with the mode of action. People freak out over plane crashes while happily getting into their cars despite the fact that planes are by every metric definably safer per capita per trip. However, when planes do crash they kill a bunch of people all at once. With cars, heart attacks, etc ... the same (or many more) people die, but over an extended period of time. HIV kills slowly - it takes years to die and the spread of deaths means they don't happen all at once. It is the car crash. When the Influenza virus kills, it kills quickly. It is the plane crash. Does that mean we shouldn't be working on finding cure or vaccine or continue working on treatments for either one? Of course not - in fact much of the same people Shloulet condemns for scientific inquiries into the Flu virus are the same people working on HIV research (and working on it very hard I might add).
However, if we were to get an epidemic of a virus with anything above a couple percent mortality over short timescales with high (arial) communicability the result would be catastrophic. Europe took decades (if not not centuries depending on the historian's point of view) to recover from the various waves of the Black Death. If we had such a pandemic with similar mortality rates and no vaccine with air/bus/train/car travel and an arial virus, then it would be a huge shock to our infrastructure to have that many people die
at the same time. That's the key. Everyone dies eventually, but if all of them die over the course of a year or two, our medical and economic infrastructure would have a difficult time handling that (read completely incapable). And from those cases of humans infected by H5N1, the mortality rate has been 50% - regardless of the underlying health of the individual. Like H1N1, it doesn't kill just the weak or the infirm (well technically neither HIV nor influenza are usually the direct causative agents of death - those are typically the secondary infections). What this research has shown is that the virus has the capability of maintaining that mortality rate while becoming communicable. As I outlined above, I still think the more likely scenario is that the mortality rate from a communicable strain derived naturally would drop, but its starting position is 50%, so it has a large amount it can drop to and still be horrific. So should a pandemic of H5N1 break out - it would be better to be as prepared as one can be. This doesn't mean everyone should already start walking around with masks, but trying to predict what it will look like and develop potential vaccines would seem a prudent step to take.
