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Is Ebola Evolving into a Deadlier Virus?

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Re: Is Ebola Evolving into a Deadlier Virus?

#61

Post by jazoom »

davidhyde wrote: post #31

> Ebola virus is a microscopic parasite that replicates inside the cells of a host A lot of the terminology used in this article is confusing. My understanding is that you get viruses (dead and tiny), bacteria (alive but small) and parasites (alive and usually bigger than bacteria). The author also talks about particles a lot as if the Ebola virus was only the rna and the particle was its trogan horse. I thought that…

I don't know where your definition of parasite has come from but I've never heard it. Also, it's not universally agreed upon whether viruses are living or non-living (dead is the incorrect term).

Parasite: an organism that lives in or on an organism of another species (its host) and benefits by deriving nutrients at the other's expense.

Sounds like a virus to me.

Re: Is Ebola Evolving into a Deadlier Virus?

#62

Post by nostrademons »

TheRealPomax wrote: post #59

Can someone post the one word tl;dr to help others decide whether this article is worth reading or not? I'm getting tired of these clickbait questions: has ebola's virulence and efficacy increased, or not? Because if it has, that title should be "Ebola is evolving into a deadlier virus", and that's entirely worth clicking through for. But if it hasn't, this is just clickbait and there are many, many more articles get…

tl;dr: Viruses mutate to become more contagious. There's some circumstantial evidence this may have happened in the 2013/2014 West African Ebola outbreak. The Kivu outbreak has ~600 hosts in which the virus is mutating right now. The article doesn't address lethality at all.

(IMHO, all of the useful information in the article is in the first sentence of the tl;dr.)

Re: Is Ebola Evolving into a Deadlier Virus?

#63

Post by kevin_thibedeau »

chiefalchemist wrote: post #28
Nasrudith wrote: post #22

Really if Ebola is to be more deadly in absolute terms it ironically should be far less lethal and disturbing in symptoms. If it was weakened to be say about as bad as the flu in terms of lethality its kill count would be way higher. Ebola is so lethal it would practically have to cause the deceased to autocremate and destroy the remains to be any worse at spreading. Killing your host quickly is a bad for a parasite…

> "Killing your host quickly is a bad for a parasite" Exactly. If the virus mutates such that the time before symptoms appear gets longer that's bad for the rest of us. But if it's the opposite (i.e., it kills faster), then that's good news and it will - in theory - eventually burn itself out.

Humans aren't the primary host so exceptional virulence isn't necessarily contained by evolutionary pressure.

Re: Is Ebola Evolving into a Deadlier Virus?

#65

Post by Fomite »

LgWoodenBadger wrote: post #56
cm2187 wrote: post #9

Earlier quoted context omitted.

Not an epidemiologist, but I understand it mostly has to do with the means by which the virus is transmitted. Ebola is very lethal but requires physical contact of bodily fluids for transmission, which contains a lot its spreading. You can probably sit on a plane next to a contaminated person and you will be fine. That contains a lot the contagion vs a virus like the flu.

Transmissibility depends on strain, based on the book Hot Zone. Ebola Zaire was transmitted only through fluids, while Ebola Reston was airborne. Though maybe the differences are by-products of the poor models mentioned in another comment.

Hot Zone is...not a good book.

Re: Is Ebola Evolving into a Deadlier Virus?

#66

Post by Fomite »

faitswulff wrote: post #6

Tangential, but if a virus's contagion is regulated by its virulence (that is, very deadly viruses are less contagious because they kill their hosts) does that mean widespread access to modern medicine could remove the upper bound on virulence by keeping the hosts alive? I could probably formulate this question better, but the basic question is, "could virus's symptoms be getting worse in general?"

Deadly viruses are not necessarily less contagious. Contagiousness has to do with a lot of things, including the duration you're able to transmit it (which is sometimes related to virulence because you're dead), the mode of transmission, and the setting its in.

Re: Is Ebola Evolving into a Deadlier Virus?

#67

Post by Fomite »

Nasrudith wrote: post #22

Really if Ebola is to be more deadly in absolute terms it ironically should be far less lethal and disturbing in symptoms. If it was weakened to be say about as bad as the flu in terms of lethality its kill count would be way higher. Ebola is so lethal it would practically have to cause the deceased to autocremate and destroy the remains to be any worse at spreading. Killing your host quickly is a bad for a parasite…

Keep in mind that, unlike The Hot Zone and modern media depictions of Ebola, we know via the West African outbreak that Ebola most commonly manifests as fever, malaise, and diarrhea.

The whole "Ebola victims are bags of blood ready to explode!" thing is...not really true.

Re: Is Ebola Evolving into a Deadlier Virus?

#68

Post by Fomite »

kevin_thibedeau wrote: post #63
chiefalchemist wrote: post #28

Earlier quoted context omitted.

> "Killing your host quickly is a bad for a parasite" Exactly. If the virus mutates such that the time before symptoms appear gets longer that's bad for the rest of us. But if it's the opposite (i.e., it kills faster), then that's good news and it will - in theory - eventually burn itself out.

Humans aren't the primary host so exceptional virulence isn't necessarily contained by evolutionary pressure.

This.

Re: Is Ebola Evolving into a Deadlier Virus?

#69

Post by Fomite »

taneq wrote: post #24

I thought (ironically) that Ebola would evolve into a less deadly virus, because that would improve its contagion rates. It doesn't care if it kills us (in fact it'd probably rather not). For a virus, the perfect balance is making is making us as sick as possible (ie. using as much of our resources as possible) without actually staying home from work.

This only matters if Ebola's primary selective pressure is from human hosts. If not, it doesn't matter. There are plenty of viruses that will kill a secondary host dead, but live swimmingly well in their primary host.

Re: Is Ebola Evolving into a Deadlier Virus?

#70

Post by Gibbon1 »

taneq wrote: post #24

I thought (ironically) that Ebola would evolve into a less deadly virus, because that would improve its contagion rates. It doesn't care if it kills us (in fact it'd probably rather not). For a virus, the perfect balance is making is making us as sick as possible (ie. using as much of our resources as possible) without actually staying home from work.

I think there is a difference between endemic viruses and zoonotic ones.

Viruses that primarily infect humans have competition between strains. What I've read is how that plays out depends on the mode of transmission vs host immunity. Things can be driven either way. Whichever strain infects hosts with no immunity first tends to win the game[2]. It's infection blocks the other strains. Because immunity means reinfection by another strain is delayed, difficult, or impossible due to immunity[1]. Sometimes less virulent is how you win (common cold) and sometimes more (cholera).

On the other hand I think Ebola has never been an endemic virus, it's a zoonotic virus. So it's accidental how virulent and deadly it is.

[1] Which is how vaccines work. I think the live polio vaccine was used because it's transmissible. Not only do vaccinated people develop immunity, but unvaccinated people catch it and also develop immunity.

[2] Read an article on Cholera. It mentioned in Northern Mexico there are some strains that have evolved to be really really weak. Weak enough to evade detection by public health authorities.

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