# 2037
Helen Branswell brings us an informative look at a study, just published in PLoS (Public Library of Science) Pathogens, that looked at how human and avian flu viruses might combine, or reassort, into new strains.
For those interested in the full study, it is entitled :
Genetic Compatibility and Virulence of Reassortants Derived from Contemporary Avian H5N1 and Human H3N2 Influenza A Viruses
Li-Mei Chen#, C. Todd Davis#, Hong Zhou, Nancy J. Cox, Ruben O. Donis*
Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
For us mere mortals who want an easier to read and understand synopsis, we have Helen Branswell's reporting. This is just an excerpt, follow the link for the entire article.
Sunday, June 1, 2008
Study shows hybrids of bird flu and human flu viruses fit well, could occur
Helen Branswell, Medical Reporter, THE CANADIAN PRESS
TORONTO - An experiment mating H5N1 avian flu viruses and a strain of human flu in a laboratory produced a surprising number of hybrid viruses that were biologically fit, a new study reveals.
And while none of the offspring viruses was as virulent as the original H5N1, about one in five were lethal to mice at low doses, showing they retained at least a portion of the power of their dangerous parent.
The work suggests that under the right circumstances - and no one is clear what all of those are - the two types of flu viruses could swap genes in a way that might allow the H5N1 virus to acquire the capacity to trigger a pandemic. That process is called reassortment.
"This study is just showing exactly that: There is a risk this virus can successfully reassort with a human virus," said Richard Webby, director of the World Health Organization's collaborating centre for influenza research at St. Jude Hospital in Memphis, Tenn.
"The problem is we don't know at this stage whether there's a benefit to these H5N1 viruses in doing that."
Nor can anyone say why, if the viruses swapped genes so readily in the laboratory, that hasn't seemed to have happened in the parts of the world where H5N1 has been circulating for years.
In what was a bit of a surprise, scientists were able to create an unexpectedly large number of biologically fit human/avian hybrid viruses in the laboratory out of an avian H5N1 and a human H3N2 virus.
Nearly half (28) replicated at nearly the same rate as the unaltered H5N1 virus. One reassortment, H5N2, was very nearly as virulent as the current H5N1 virus.
The good news is that most of these hybrids demonstrated less lethality in mice than the unadulterated H5N1 virus, giving at least some hope that a hybrid strain might end up being less virulent than the current H5N1 strain.
The big unanswered question remains transmissibility among humans, and while advances are being made in our scientific knowledge, we truly don't understand all of the variables involved.
