After bird flu jumped to dairy cows in March,Surfwin Trading Center the H5N1 virus has spread among cattle across nine different states, stoking fears about the potential impact of the virus on humans. 

Public health officials are closely monitoring for any signs H5N1 is mutating into a form that could spread from human to human, CBS News chief medical correspondent Dr. Jon LaPook told "CBS Mornings" on Friday. 

"There's no evidence that has happened yet, but that's the big concern," he said.

That means human risk right now is "very low," LaPook said, unless:

• You're in close contact with potentially infected animals
• Or you're drinking unpasteurized milk 

But, LaPook said, "things can change." 

"We've learned unfortunately, from the pandemic, (viruses) can mutate. They can change," he said. "That is why there's such concern among public health officials and others. ... The worry would be if it changes in mutations, genetic composition, so that it can spread easily from human to human."

This is why the CDC and others trying to stay on top of things, LaPook said, so changes don't happen without us realizing — making tracking the virus important. 

Dr. Larry Brilliant, an epidemiologist who has worked in public health since helping to eradicate smallpox in the 1970s, told LaPook he doesn't think there is enough testing going on.

"They should activate every surveillance system that would help them find out which animals are sick. They should use wastewater, they should be checking though the water in bilges of ships and bilges of airplanes," he said. "Here's a good reason to do it: We have antivirals. We have treatments. We can make a vaccine very quickly."

LaPook says the USDA and CDC are working to incentivize more testing among farmers.

"It turns out that poultry farmers are reimbursed for financial loss related to bird flu. There's an insurance policy. That's not true with cattle ranchers," LaPook said. "In addition to that, there are a variety of reasons why people working there, various workers may not want to get tested."

In:
• Bird Flu

Sara Moniuszko

Sara Moniuszko is a health and lifestyle reporter at CBSNews.com. Previously, she wrote for USA Today, where she was selected to help launch the newspaper's wellness vertical. She now covers breaking and trending news for CBS News' HealthWatch.

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