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Bird flu virus possibly found in a handful of wastewater sites, CDC says

Influenza A was detected at higher-than-average levels in five states.
In an aerial view, pools of water are visible at Central Marin Sanitation Agency wastewater treatment plant
Wastewater samples from across the U.S. overall show low levels of influenza nationally. Flu experts, however, remain vigilant. Justin Sullivan / Getty Images file

There’s no solid evidence that bird flu is spreading among people, the Centers for Disease Control and Prevention said Tuesday amid an outbreak of the virus in dairy cows.

New data from 189 of the agency’s wastewater sampling sites showed that as of May 4, an influenza A virus had been detected at higher-than-average levels in a handful of sites across the country, including in Alaska, California, Florida, Illinois and Kansas.

The bird flu currently circulating in cows, called H5N1, is a type of influenza A.

Just one site, in Saline County, Kansas, showed notably high levels of flu virus for this time of the year. Four herds in Kansas tested positive in April, the CDC said.

It’s unclear whether the Kansas wastewater samples were limited to human waste or whether they included runoff water from farms. It’s also unclear whether the high levels of virus in the wastewater indicate infections in humans, cows, birds or other animals. There hasn’t been any unusual uptick in flu-like illnesses in recent weeks, the CDC said.

“We’d really like to understand what might be driving that influenza A increase during what we consider the lower transmission season for influenza A,” said Jonathan Yoder, deputy director of the CDC’s division of infectious disease readiness and innovation.

A representative from one of Saline County’s major hospitals didn’t respond to a request for comment.

Dr. Cameron Wolfe, an infectious disease expert and an associate professor of medicine at the Duke University School of Medicine in North Carolina, said the new CDC data “is actually pretty reassuring.”

“We’re in the middle of May,” he said, when “there isn’t naturally a lot of flu.” Wolfe said he isn’t seeing any uptick in flu-like illnesses in his medical practice.

As of Tuesday, 42 herds in nine states — Kansas, Colorado, Idaho, Michigan, New Mexico, North Carolina, Ohio, South Dakota and Texas — had been affected.

The agency is monitoring 260 people who have been exposed to infected dairy cows for flu-like symptoms. Thirty-three people have been tested for the virus. So far just one person — a dairy farm worker in Texas — has been diagnosed with bird flu connected to the dairy cow outbreak. He developed a severe case of conjunctivitis, or pinkeye, and has recovered.