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Comment by gburt | Hacker News Reader

This is a clear win for "public health", leaving just one strain (WPV1) which is geographically constrained.

A question for those well-versed in the biomedical and ecological sciences: Could our attempts to eliminate viruses be a bad thing? I wonder about the ripple effects of ecosystems on each other. We do not brag about extinction of any other natural entity.

And, when eradication does not work, when we only hinder the growth of a virus, does the attempt to prevent infection (or any form of "mostly cleaned up" coverage) encourage the development of superviruses by selecting for the strongest in the set, in the same way bacteria do? If not, why?

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Not really, no. The "niche" that pathologic microbes play is basically entirely negative. Any supposed benefits are certainly well drowned out by massive mortality and morbidity. Nobody cries for mass murderers.

To your second question, that can be a big problem. HIV is probably the best example. Patients receiving HAART can really hurt themselves if they skip a treatment; it gives the virus enough time to mutate and get ahead. Usually this works at the individual level because of the mutation rates in viruses - and their tendency to revert upon infection to a new host - but theoretically yes. Moral of the story? Always take all your drugs.

Couldn't the second problem be solved with bacteriophage therapy?

How? Phage therapy — which, let's be real, isn't accepted anywhere outside of Russia, Georgia, and Poland(?) — would only help against bacterial pathogens. It's useless against other viruses.

"And their tendency to revert upon infection to a new host" - Are you saying that viruses revert to some sort of "base version" when they transfer from host to host? I'd never heard of such a thing. How would that work?

New hosts don't take drugs that kill certain variants of the virus, so the version that does best in a drug free environment replicates quickest. That's usually different from the version that does best in the drugged environment.

Yes. Depends on the virus, but in the case of HIV infection, the patient can produce over 1 billion new virus particles a day. Given the size (10kb) and mutation rate (10-3 to 10-6, iirc) every single nucleotide is mutated every single day.

There's more to it than that (lookup "biological filter" for example), but the virus must mutate to avoid drugs, which usually means a fitness hit (lower replication, for example). Upon infection of a new host, the virus can quickly maximize fitness once again. Not a "base version" per se, but a more ideal, fit virus, without many/most of the escape mutations.

If that is the case, then would it be possible for someone who skipped a dose and development a resistant strain, to continue skipping doses until his virus looses its resistance?

Polio is species specific to humans (at least, the strains we are eliminating are), so the ecological impact is limited to the indirect effects that come from more, healthier humans.

I've read/heard some discussion about how humans suffer detriment now that we no longer have gut parasites living with us. Unfortuntely it's been rather thin on the ground, I suppose it's not a very glamourous area to study.

See An Epidemic of Absence: A New Way of Understanding Allergies and Autoimmune Diseases: http://www.amazon.com/dp/B0061P2L5U

I was thinking of the exact same thing. But I'm not sure it really applies, at least in the specific case of polio. Historically most people didn't have it, so we can't really be "missing" it. If we were talking about eradicating something relatively common and non-lethal, such as the common cold, that would be more comparable to the gut parasites.

For polio, the hypothesis is that it was very common before 1900. I quote from "From Emergence to Eradication: The Epidemiology of Poliomyelitis Deconstructed" http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2991634/

> In the pre-epidemic era, enteric infections were so ubiquitous that most infants were infected within 6–12 months, at a time when they had circulating antibodies passively derived from their nursing mothers. Although serum antibodies did not prevent enteric infection, they were sufficient to preclude viremia, thereby avoiding invasion of the central nervous system and paralysis. The result was the acquisition of active immunity under the cover of passive protection.

So the hypothesis is that historically most people did have it and were immune, and only the improved hygiene past 1900 led to epidemics. We can indeed ask whether some individuals are worse off now because they didn't contract it in their infancy. But we're also doing pretty much the same thing with the vaccinations. Maybe we'll see a rise in allergic reactions when polio 2 vaccines are phased out. I don't think that anybody would advise infecting babies to get the benefits back though :-)

I stand corrected. Very interesting, thanks!

It's complicated, but the science is fairly well established that lack of parasitism has lead to increased incidence of allergies in developed nations. Small price to pay.

Autoimmune disorders are a large category - there's also some evidence that autism-spectrum disorders are caused by autoimmune responses in the mother.

Also keep in mind parasites and gut bacteria are far different to infectious diseases like polio and measles.

We are rapidly approaching an era of medical treatments where giving a treatment of "probiotics" to correct your newborn child's gut bacteria in order to prevent asthma much the way we give immunisations against diseases today. The hygiene hypothesis is getting some pretty compelling evidence and hopefully it will lead to us learning the "right" kind of things we should be exposing our children to in order to prevent these autoimmune conditions.

Interesting question.

I would argue that viruses have an obvious impact into our human ecosystems. Losing a father, a mother, a sister, a teacher, a doctor hurts not only the person, but us all. So I would only argue for the preservation of viruses in the wild if they, somehow, had an even larger provable impact in the long run.

Also keep in mind that we don't need to eliminate viruses entirely, we can keep some samples in labs. So we aren't losing that much in term of potential scientific knowledge and we can always reintroduce them if we feel like. This is much harder to do with, say, polar bears. Once they are gone, they are gone for good. So it is in our best interest to preserve them in the wild. At least, until we figure out cloning or cryogenics.

One comment. With bacteria, resistance is to specific (or multiple) antibiotics. This doesn't mean necessarily that the strongest bacteria in general terms get selected. For example MRSA tends to affect people who for some reason have weakened immune systems because healthy people do a decent job of fighting it off.

Good point. My use of the word "strongest" was definitely misleading, but I am not convinced it is always the case that there isn't a relatively low dimensional definition of "strong" in this sense.

I think (and if I'm wrong someone please correct me) that adaptations the bacteria evolve are specific features to specific pathways that they have for removing toxins (to a bacteria an antibiotic is a strong toxin).

It depends on what you meant by pathway:

https://en.wikipedia.org/wiki/Antimicrobial_resistance#Mecha...

The mechanism can be encoded on a plasmid, for example:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC514751/

So in that case, a bacteria could import the mechanism wholesale from a resistant population.

(Plasmids are fragments of DNA that bacteria can swap back and forth, even across species)

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