Scientists Move Closer To Understanding Bird Flu
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SINGAPORE — Scientists tracking bird flu moved closer to understanding the evolution of the viruses and the genes that make them more infectious to people in a new study.
About 52 key genetic changes distinguish avian influenza strains from those that spread easily among people, according to researchers in Taiwan, who analyzed the genes of more than 400 A-type flu viruses. The analysis will help scientists trace the mechanism for infection and how the viruses replicate in different species, according to a report appearing in the September edition of Emerging Infectious Diseases.
Interest in influenza viruses has been bolstered by the spread of the H5N1 avian flu strain, which has infected at least 241 people in 10 countries during the past three years, killing 141 of them.The virus may kill millions if it changes into a pandemic form that can be passed between humans.
“How many mutations would make an avian virus capable of infecting humans efficiently, or how many mutations would render an influenza virus a pandemic strain, is difficult to predict,” Guang-Wu Chen and colleagues at Taiwan’s Chang Gung University wrote.
The researchers analyzed the gene sequences of 306 human and 95 avian influenza viruses to molecularly identify the host species. The data was crosschecked with 15,785 more sequences from the National Center for Biotechnology Information.
“It is the type of work that everyone has thought of doing, but no one has had the time to do,” a virologist at the Erasmus University in Rotterdam, Ron Fouchier, said in an e-mail today. “The number of mutations in the viruses that correlate with host species is much larger than I initially suspected.”
Dozens of influenza subtypes exist, many of which were not analyzed in the study. This may have influenced findings, Mr. Fouchier said.
“Using reverse genetics technology, and with the information collected from the systematic analysis of mutations in published genome sequences as described in this paper, it should now become possible to test the effects of each of the described mutations and start to understand how avian influenza viruses adapt to the human host,” Mr. Fouchier said.