Other pandemic threats are lurking in H9 virus

H5N1 isn't the only avian virus that threatens to trigger a pandemic. A group of virologists was able to make an H9 virus much more transmissible by changing a single chemical component in the hemagglutinin protein, which allows the virus to attach to cells. Mixing bird flu genes with the human flu virus also made H9N2 more threatening to humans. The scientists were working with ferrets in the study, which offer an effective animal model for determining human responses.  

"The H9 may be a silent virus that doesn't get noticed until it's too late," says Daniel Perez, a virologist at the University of Maryland.

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