Tuesday, August 25, 2009

Triple Reassortment Swine Influenza*

*aka Triple Reassortant Swine Influenza

"Six of the eight genetic segments of this virus strain are purely swine flu and the other two segments are bird and human, but have lived in swine for the past decade."
---Raul Rabadan, PhD, computational biologist at Columbia University

And that is why pigs are dubbed "mixing bowls" for influenza viruses. While humans are susceptible to human influenza viruses and somewhat less so to the swine varieties (at least up until now), our airways don't provide particularly good handholds for those influenza subtypes that seek out birds. Pigs, on the other hand, have receptors on the surfaces of their tracheal cells that welcome strains from all three species. From porcine throats and lungs, therefore, emerge new flu varieties with the potential to cause dangerous human disease.

These new flus are called triple-reassortment swine influenza A viruses as they contain genetic material from bird, human, and pig influenza viruses. Until recently, the pigs of North America kept their flu to themselves with sporadic reports of human infections generally limited to those most exposed to pigs in their daily work. Now, however, with another flip of their surface proteins--and flu viruses reproducing every 8 hours have 3 opportunities per day to mix, match, and mutate their DNA in a promiscuous sort of way--the little swinish devils have brought these reassorted flus to human airways. Furthermore, this newest genetic triple threat passes easily from one infected human to another.

With all this mating and mutating, therefore, epidemiologists are finding it hard to predict what's in store as the swine flu (and it is a swine flu no matter what it's called, passed at first from live pigs not pork meat) makes it way back to the Northern hemisphere big time. Fortunately, vaccine production is underway, and immunization programs should begin next month. More on that soon.


Mauigirl said...

Sorry for not being around lately, am finally catching up with my blog reading.

Thanks for an interesting and informative post on swine flu! I hope they get that vaccine ready in time. (Of course being one of the older people I'm less susceptible to it than the younger ones. There are some advantages to age!)

Ruth said...

I guess those old Hebrew food laws made sense...
Seriously, I wonder if changes in farming methods, where large number of similar animals are kept in close quarters, has contributed to changes in transmission rates?

Anonymous said...

scary stuff... do you know if this swine transmission to humans, etc. applies to just one or two pigs,say, living alone, or does it happen when they are in a group living situation, or what? Should we destroy all pigs, like some countries (I think it was greese) have?
Are they sure it isnt transmittable after cooking?
I know the jewish traditions ban all eating of swine,etc... but the Christian religions say that was lifted... except some say the blood prohibition was not lifted. Now I hear Isrealies are all about saying 'I told you so" about swine and swine flu....
I think it is difficult to sort out fact from fiction, regardless of the religion... how is anyone suppose to know?
"I told you so".... not really! What does that mean? Clear as Mud....
Do you have an opinion on this?

femail doc said...

Hi MG, thanks for stopping by--I'm always happy to get your comments.

Ruth: I have no doubt that large amounts of animals raised for slaughter does not promote the health of the animals, their tenders, nor the people who eat them. Check out "Dying for a Hamburger" for sobering theories on cow-related prion disease.

Anon: The safety of pork-related products with respect to swine flu is quite clear. I am very comfortable with pork, don't really know what to say about tending an isolated pig or two in the backyard, and would avoid a career as a pig herder or geese tender at this time.