Why The Mixture?

April 26, 2009 3:00 PM

Current Events Science Filter: Both the AP and Reuters are reporting that the Swine flu actually "contains DNA from avian, swine and human viruses, including elements from European and Asian swine viruses." Can someone please explain to me how such a mixture is possible? Thanks.
posted by ornate insect to health & fitness (7 answers total)

Antigenic shift.
posted by Cool Papa Bell at 3:11 PM on April 26, 2009

Related follow up question: how possible is it to pinpoint the origination of an outbreak of a new strain like this? For instance, there appears to be some unverified reports in Mexico that "the disease vector was a type of fly that reproduces in pig waste and that the outbreak was linked to the pig farms."
posted by ornate insect at 3:30 PM on April 26, 2009

Someone already posted, antigenic shift.

Pretty neat concept really. Influenza viruses contain 8 DNA segments, but it doesn't package them all that specifically, so 2 different virus particles infecting one cell can give rise to virus particles with all sorts of combinations of the original 16 segments (8 from each).

Pigs are our downfall, essentially. Most bird flus cannot infect humans, but both bird flus and human flus can infect pigs. Take a pig, give it both a bird and human flu, and when the viruses reproduce, you can get mixing of the bird flu DNA and human flu DNA into the viruses that are produced.
posted by davidnc at 4:00 PM on April 26, 2009

An insect vector associated with this flu would constitute a Very Bad Sign:

In short, a reduction in host mobility should be especially costly for parasites that rely on host mobility for transmission; these parasites, then, should have lower levels of virulence. However, if transmission of the parasite is less affected by host mobility, the parasite's fitness should not be greatly affected by the immobilization of the host, and natural selection should favor a higher level of host exploitation and greater virulence (Ewald, 1995). ...
posted by jamjam at 4:03 PM on April 26, 2009

how possible is it to pinpoint the origination of an outbreak of a new strain like this?

Not an expert on influenza, but certain H-N combinations on the surface of the virus are more prevalent in (and sometimes exclusive to) particular species. H1N1, for example, is more common in pigs, while H5N1 identifies the avian influenza that everybody is still worried about (with good reason). As for tracking it down, the WHO does a lot of detective work, in collaboration with hospitals and various monitoring agencies situated world-wide. I've seen the director of the Australian-based collaborating centre (here) talk about what they do. It's a very impressive outfit. They are constantly being sent viruses from hospitals nation-wide (and world-wide, for that matter), which they they phenotype and put into a massive database that effectively allows the tracking of new and pre-existing viral strains in a relatively rapid fashion.

More information on the WHO website.
posted by kisch mokusch at 4:15 PM on April 26, 2009

It's pretty neat, isn't it? Those viruses are creepy little buggers. Want to be even more scared? Look up cytokine storm.
posted by gjc at 4:42 PM on April 26, 2009

Cytokine storm is just another case of your body doing the something that makes sense on a scale that doesn't. Sort of like going into shock to avoid bleeding to death.

I've worked on, I think it's four drugs now, that might have been useful for septic shock. No joy yet.
posted by Kid Charlemagne at 8:56 PM on April 26, 2009