Four more farmworkers in Washington have been infected with bird flu, adding to the 31 cases across six states. While experts say the risk of a human pandemic is low, the virus's spread among animals, especially cows, worries them. Washington's veterinarian, Dr. Amber Itle, explains the concern: "The longer the virus stays in animals, the more it evolves, and the more worried we get about a pandemic. "

Washington's health secretary, Dr. Umair Shah, says so far, the virus hasn't changed enough to spread easily between people. Workers on the affected Washington farm wore protective gear, but still got sick with mild symptoms. A puzzling case in Missouri is under investigation.

Scientists like Dr. Richard Webby warn that cows, which shed a lot of virus in their milk, could help the virus mutate. They're also concerned about the upcoming flu season, as two viruses in the same host could swap genetic material and mutate faster.

Dr. Peter Rabinowitz urges better protection for farmworkers and stresses the importance of flu shots. Washington recently found dead wild birds, indicating the virus's spread. Nationwide, over 103 million birds have been affected.

More Farmers Infected: Bird Flu Concerns Grow

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