Ebola

[IUHoosiergirl88]

Originally Posted by als463

After complaining about being sick of hearing about Ebola, I was really intrigued by your background and interest in it. I have to ask as I am no expert in biology, why is it considered the most 'perfect' virus? Is that because it's hard to detect or something?

So the 'perfect' virus is one that's highly contagious so it's easily transferred from host to host, is shed/released very rapidly by the host (via sneezing, coughing, sweat, pus, whatever), evolves quickly to get around both the immune system and medical countermeasures, evokes limited immunity so you can get the same virus over and over, and is only moderately virulent so it doesn't kill off all potential hosts. Ideally, they're also pretty environmentally stable, but that's able to be bypassed--just look at influenza's seasonal outbreaks. You may also want a virus that lays 'dormant' in the host while still remaining infective, so you can pass it on to others even if you yourself are not showing any ill effects.

Ebola fits a lot of those criteria, but not all of them. It's highly contagious because it requires a low viral load (i.e. the amount of virus you come in contact with) to infect, but it's not airborne so it's not transferred as easily. Patients do shed high viral loads--check. It doesn't mutate THAT rapidly when compared to other viruses--but there's not a good treatment for it at this point. It does invoke limited immunity, but it's appearing like that immunity may be stronger than we think. Finally, it's pretty virulent and obviously kills off a high percentage of its hosts, so eventually it 'burns out.'

Norovirus, on the other hand, is INCREDIBLY contagious, you shed high viral counts (some studies have shown 10^5 to 10^11 viral copies per gram of poo or vomit), it mutates extremely fast, immunity is pretty much nonexistent, and fits that moderate virulence category. It's also extraordinarily stable.

Interestingly enough, when it comes to viruses, you actually don't want high virulence because oftentimes, with that comes decreased infectivity or contagiousness.

[als463]

Originally Posted by IUHoosiergirl88

So the 'perfect' virus is one that's highly contagious so it's easily transferred from host to host, is shed/released very rapidly by the host (via sneezing, coughing, sweat, pus, whatever), evolves quickly to get around both the immune system and medical countermeasures, evokes limited immunity so you can get the same virus over and over, and is only moderately virulent so it doesn't kill off all potential hosts. Ideally, they're also pretty environmentally stable, but that's able to be bypassed--just look at influenza's seasonal outbreaks. You may also want a virus that lays 'dormant' in the host while still remaining infective, so you can pass it on to others even if you yourself are not showing any ill effects.

Ebola fits a lot of those criteria, but not all of them. It's highly contagious because it requires a low viral load (i.e. the amount of virus you come in contact with) to infect, but it's not airborne so it's not transferred as easily. Patients do shed high viral loads--check. It doesn't mutate THAT rapidly when compared to other viruses--but there's not a good treatment for it at this point. It does invoke limited immunity, but it's appearing like that immunity may be stronger than we think. Finally, it's pretty virulent and obviously kills off a high percentage of its hosts, so eventually it 'burns out.'

Norovirus, on the other hand, is INCREDIBLY contagious, you shed high viral counts (some studies have shown 10^5 to 10^11 viral copies per gram of poo or vomit), it mutates extremely fast, immunity is pretty much nonexistent, and fits that moderate virulence category. It's also extraordinarily stable.

Interestingly enough, when it comes to viruses, you actually don't want high virulence because oftentimes, with that comes decreased infectivity or contagiousness.

This was all really informative. Thanks for sharing, IUHoosiergirl88.