The Pathogen to End Mankind -- To Far From Reality?

[Ailurophobia]

Popular game pandemic has conquered the iPhone market. Owned by many people, the game's point is in essence to kill every last human being on earth...but would a disease actually do this? To start, a disease is really only ever as deadly as it needs to be. Virulence, the level of how deadly a disease is is primarily determined by how much a disease needs or doesn't need to spread. The cold for example, has little to no side-effects because it's very easy to spread and gains nothing from hurting you. Something like Ebola would be on the opposite end of the scale. So in theory, if the cold was given to everyone, would it become harmless? Evidence suggests that such has happened in the passed through viruses actually becoming part of our genetic code with up to 8% of our current genome being viruses according to Sharon Moalem in Survival of The Sickest. If a virus were to kill every last human on earth, that would be the end of that virus...

However, there is a flaw in that theory because if a disease were to spread before it could adapt to become less virulent could it actually end itself...? I'd like to hear what all of you guys think.

 

Also to consider: things that have wiped out mass majorities of people in the past such as the black death.

[CharonY]

It is true that over any significant length of co-evolution pathogens tend to mellow out a bit (at least it appears to be the case in viruses), partially because killing the host is not a very good long-term strategy. However, pathogens generally do not modulate their virulence as response, it is merely a matter of selection. Adaptation is in essence a passive mechanism, i.e. those strains that kill their host fast tend to spread slower than the others over evolutionary time scales. But if spreads fast, there is a chance that it kills of its host before any kind of selective pressure could kick in.

 

That being said, whether that could happen in any population depends on a lot of other factors, including size of the host populations, migration and so on. Humans are quite abundant and wide spread, so there is a good chance that pockets of survivors will exist and/or that there are people who will be immune, for example

[Popcorn Sutton]

I think that we have done a very good job at surviving. That's something that our species does really good.

[Roamer]

 

 

However, there is a flaw in that theory because if a disease were to spread before it could adapt to become less virulent could it actually end itself...?

 

This is a reason why we often try to quarantine a disease.

[Ailurophobia]

 

This is a reason why we often try to quarantine a disease.

Quarantine does not secure protection against disease.

It is true that over any significant length of co-evolution pathogens tend to mellow out a bit (at least it appears to be the case in viruses), partially because killing the host is not a very good long-term strategy. However, pathogens generally do not modulate their virulence as response, it is merely a matter of selection. Adaptation is in essence a passive mechanism, i.e. those strains that kill their host fast tend to spread slower than the others over evolutionary time scales. But if spreads fast, there is a chance that it kills of its host before any kind of selective pressure could kick in.

 

That being said, whether that could happen in any population depends on a lot of other factors, including size of the host populations, migration and so on. Humans are quite abundant and wide spread, so there is a good chance that pockets of survivors will exist and/or that there are people who will be immune, for example

Yes, but then again diseases evolve more quickly in the scale of things. Adaption may be passive but within a matter of days a disease can change dramatically, and within months/years a disease could perhaps even switch target species. A disease may not even evolve down the path of lower virulence when it could spread and adapt off humanity and then target another species.

[CharonY]

It appears that you are switching positions from the original OP. There your argument was that whether evolution would render pathogens harmless before they could kill off their hosts and as a consequence:

 

 

So in theory, if the cold was given to everyone, would it become harmless?

I was arguing against that scenario as the selective pressures to become less virulent would require large time scales and hence if the cold was given to everyone it would just as it did before. Pathogen populations do not rapidly undergo vast changes (though their generation time is obviously on the scale of other bacteria). I.e. if everyone got the cold there are likely a couple of bacteria in the total population that are more or less virulent, but then you have the massive amount of bacteria who are not. It will take time until the frequencies shift perceptibly.

[Edwina Lee]

I think it does not need a genius to figure out how to wipe out all humans with viruses. As such, humans are already at risk of someone doing just that.

As for natural evolution, a disease agent has to evolve the ability to infect as well as to kill to accomplish that task. It has got to be able to infect everyone universally like the common cold, which already has that ability.

To kill off the entire human species, it needs to survive quite a long time to get itself infecting, but without invoking a deadly immune response from the human. Only at some later time would it become virulent.

 

Such diseases already exist. I understand that STIs (sexual transmitted diseases) usually has no external symptoms.

 

If the virulence is evolved quickly to kill level, then it could be the end of humans. One just hopes it won't happen.

[Edwina Lee]

What do you know, someone has already tried quite recently!

 

2014-08-21 Lady Al Qaeda has just been sentenced to an 86 years jail term for pening the Ebola bomb among other things for the US

http://www.dailymail.co.uk/news/article-2731164/ISIS-offered-swap-Foley-Lady-Al-Qaeda-Terrorists-wanted-return-MIT-graduate-jailed-U-S-planning-mass-casualty-strike-dirty-bomb-ebola-chemical-weapon-spared-children.html