Science a GoGo's Home Page Forums General Discussion General Science Discussion Forum Why would a retrovirus kill its host?

I'm not a microbiologist, just a retired computer scientist.

For years I have asked myself why the highly evolved genetic programming in a retrovirus MIGHT include as a survival strategy the possibility for voluntarily killing its host along with itself.

Today I was following NOVA Science on PBS and a researcher announced her discovery about how one celled bacteria can sense their numbers by communicating with each other using specific molecules as messages. It seems that not only do the bacteria want to determine the presence of like bacteria identical to them, but also the presence of bacteria different from them.

That made me wonder if retroviruses might also want to communicate amongst themselves. And might these same retroviruses also be listening for other messages that signal that it is time to kill the host?

Why would the retrovirus want to kill its host?

There must be many reasons including the unintended over consumption of the host's resources, but one new idea that came to my mind was simply that the host appears to no longer offer to the retrovirus the prospect of being able to migrate to another host before the current host dies of natural causes.

Why then would the retrovirus want to hasten the death of the host in this situation?

The only answer I can come up with is that by killing its host as soon as possible, all the other living hosts, who are all likewise lodging copies of the same retrovirus, well these other hosts might have a better chance of survival with one less living host on the planet who no longer appears to offer a reasonable opportunity for the retrovirus to migrate.

This strategy calls for many retroviruses to sacrifice themselves by killing lost cause hosts in order to encourage the survival of hosts which are genetically different and appear to (continue to) have a "characteristic" that makes these hosts good candidates for insuring the retrovirus's crutial need to migrate to new hosts via whatever the usual transmission method is.

The retrovirus wants to create a world where the only surviving hosts all have this essential "characteristic" nessessary for insuring the retroviruses long term survival which depends on migration.

If all this seems possible, then what might be the molecular message that tells a retrovirus that the host no longer appears to have the essential "characteristic"?

Do hosts, through the natural ageing process or whatever, suddenly begin to generate molecules that tip off the retrovirus that it is now lodged in a dead-end host and it is time to kill off the host for the reason I stated above?

What might that kiss-of-death molecule be?

Could this strategy apply to computer viruses as well as biological ones?

Has this idea ever been put forward before?


Thanks for your curiosity.

Wolfville wrote:
"For years I have asked myself why the highly evolved genetic programming in a retrovirus MIGHT include as a survival strategy the possibility for voluntarily killing its host along with itself."

You are assuming information not in evidence. The history of infectious diseases is that those that start off killing their hosts ... evolve to become less lethal.

But the primary reason an infectious disease might wish to kill its host if that is how it might enlarge the pool of those infected. For example if the carcass would be consumed by multiple potential hosts.

I suspect that retroviruses that kill their host probably do so because they have recently mutated or jumped a species barrier. They have not had enough time to co-evolve with the host.

Thanks for your response. I hope no one assumes that anything I am posting is founded in anyway in facts. I'm simply brainstorming to see if there is any logic to my thoughts.



I agree if the death of the host enhances the chances of the organism migrating to new hosts. But what if the death of the host is a guarantee that the organism will die at the same time.

Would it then serve any useful purpose for the organism to kill its host? I wonder if the organism could be programmed to do this only if by doing so, it would indirectly help like organisms in other hosts to better survive.

It is as if the organism has achieved the role of husbandry, selectively breeding hosts who are most suitable to the essential needs of the organism, even if the process calls for many members of the organism's family to sacrifice themselves.

But what if this retrovius, prior to mutating and/or jumping to a new specie, had spent millions of years in a symbiotic relationship in another host specie.

Could such a survival strategy have evolved purely by accident within the retrovirus, and become a permenant genetic feature in the retrovirus?

wolfville wrote:
"But what if the death of the host is a guarantee that the organism will die at the same time."

It never does. In fact some infectious disease could not survive were it not for the death of their host. Yes it may kill 99% of those organisms. But the question of whether it is advantageous does not involve any individual or group ... rather it is based on the result. Were this not true the disease organism would become extinct.

wolfville wrote:
"Would it then serve any useful purpose for the organism to kill its host?"

You are still focusing on the host in a manner not reflective of biology. The host is just a temporary host of no more significance than the water a fish swam in the day before. The host is irrelevant except in the short-term.

wolfville asks:
"But what if this retrovius, prior to mutating and/or jumping to a new specie, had spent millions of years in a symbiotic relationship in another host species.

Could such a survival strategy have evolved purely by accident within the retrovirus, and become a permenant genetic feature in the retrovirus? "

Yes. And there are plenty of examples of this being the case.

Wolfman wrote:

"Could such a survival strategy have evolved purely by accident within the retrovirus, and become a permenant genetic feature in the retrovirus?"

Wolfman. You are forgetting one very important fact. What chance does any species have for surviving to the next generation if it doesn't have some reproductive mechanism? Replication mechanisms must have evolved for it to even be a retrovirus.

Question. Can retroviruses survive in soil? Death of host certainly then an advantage.