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Flu viruses are notorious for their ability to mutate, or change, rapidly. That's one of the reasons we need a new flu vaccine each year, and the reason why a vaccine based on today's version of the H5N1 virus may not be effective against a mutated pandemic strain.
Sometimes these changes are caused by replication errors, other times, the virus picks up changes by exchanging genetic material with another flu virus, and that is known as reassortment.
Researchers have mapped the genome of samples of the H5N1 virus collected in Europe, the Middle East, and Africa, and have discovered that we now have three distinct strains, or clades, spreading throughout the western world.
The technical details are available from the Journal of Emerging Infectious Diseases and may be accessed here.
An overview, produced by the University of Maryland explains these findings in considerably less technical language.
“Bird Flu” Genome Study Shows New Strains, Western Spread
Newswise — In a paper in the May issue of Emerging Infectious Diseases, an international team of researchers report the first ever large-scale sequencing of western genomes of the deadly avian influenza virus, H5N1.
Their study of 36 genomes of the virus collected from wild birds in Europe, the Middle East and Africa (EMA), and Vietnam confirms not only that the virus has very recently spread west from Asia, but that two of the new western strains have already independently combined, or “reassorted,” to create a new strain.
Several samples also contained the mutation associated with the form of the “bird flu” that caused several human deaths in 2006. It is the virus’s ability to rapidly mutate into a pathogen that may eventually be passed between humans that concerns health officials about a worldwide pandemic of H5N1 influenza.
The study also produced some evidence that strengthens the case that humans have had an impact on the movement of the flu out of Asia.
“This is the first time anyone’s looked at all of the H5N1 genomes in the west,” said Steven Salzberg, the study’s lead author and director of the University of Maryland Center for Bioinformatics and Computational Biology. “Until now, the studies have been primarily on samples from the Far East. Our study shows that the virus is spreading west, and that there have been three separate introductions of H5N1 in Europe, the Middle East and Africa.”
New Strains Confirmed
The study’s researchers, an unusual team of scientists from 11 countries that range from U.S. to Iran, collaborated to share data and sequence H5N1 samples taken from birds in a widely dispersed geographic region that includes Nigeria, Niger, Sudan, Egypt, Afghanistan, Iran, Slovenia, Croatia and Italy.
“We found that the EMA strains of the virus are distinct from the Vietnamese and other Asian strains,” said Salzberg, “and that they have already divided into three separate new strains. One of the new strains has been the cause of several fatal human cases in Egypt and Iraq.”
The research showed that the three new strains, called clades, evolved independently and in different regions from a single genetic source. “Our analysis places this source most recently in either Russia or Quinghai Province in China,” Salzberg said.
