Comment
This is a question, not a comment, and would influence the answer to CQ6; I just want to be sure I get things right. I will be using this case in about 10 days on a class for non-science students. I just wondered if I missed something about the H1N1 so-called swine flu. Is there any evidence at all that it came from pigs? As I understand, it contains RNA segments from avian, porcine and human sources, and I have never seen anything about it being transmitted directly from pigs to humans although apparently a Canadian pig got it from a human. There was a big pig facility in the Mexican town where the first cases were found, but I have seen nothing about those pigs clearly transmitting it to humans. I used to do surveillance of avian flu viruses in Hong Kong before anyone was interested (the 80s)and we thought that the next pandemic would originate where pigs and ducks lived together on farms in SE Asia, but it didn’t happen (at least not yet).
Comments submitted February 15, 2010 by:
Susan Cure, Associate Professor of Biology
American University of Paris
scure@aup.fr
Editor’s Reply
Viruses regularly create new combinations of their DNA, exchanging pieces of DNA with other viruses.
The swine flu is actually a strain of influenza with genes from flu that infected pigs, flu that infected birds, and flu that infected people. So the name is not due to the source of infection, but to the fact that this is a new type of flu that we are not able to respond well immunologically to because we have not previously encountered the swine component of this flu’s genetics.
It sounds like the questioner already understands this, and is wondering how this flu moved into people. And that piece we don’t know. We do know that there is the pig flu, which doesn’t (normally) infect humans, and the human flu (which we have been able to resist enough that it can't develop an epidemic outbreak). Presumably an animal (either pig or human) was infected by both versions of the influenza, and while infected the two strains swapped DNA. So the virus we call H1N1 has the genes to invade human cells and manage human-to-human transmission, and also has genes from the pig variety that we don't have defenses against. Researchers have been hunting through Veracruz trying to find this answer. See http://www.cnn.com/2009/HEALTH/05/06/swine.flu.origins/index.html.
Reply submitted February 15, 2010 by:
Eric Ribbens, Associate Professor
Western Illinois University
E-Ribbens@wiu.edu
Author’s Reply
Eric’s comments are on-target. Conclusively documenting viral transmission on a specific case basis can be exceedingly difficult. The links below provide the experts’ views on the subject.
Here are my references for question CQ6 (and related slides):
Reply submitted February 15, 2010 by:
William D. Rogers, Associate Professor
Ball State University
wrogers@bsu.edu
