Bird flu virus could be detected in handful of wastewater treatment sites, CDC says

There is no strong evidence that avian flu is spreading among humans, the Centers for Disease Control and Prevention said Tuesday, amid an outbreak of the virus in dairy cows.

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

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

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

It is not clear whether the Kansas sewage samples were limited to human waste or included farm runoff. It is also unclear whether high virus levels in wastewater indicate infections in humans, cows, birds or other animals. There has been no unusual increase in flu-like illnesses in recent weeks, the CDC said.

“We would really like to understand what might be driving this increase in influenza A during what we consider to be the lowest transmission season for influenza A,” said Jonathan Yoder, deputy director of the division of influenza A. CDC Infectious Disease Preparedness and Innovation.

A representative for one of Saline County’s major hospitals did not respond to a request for comment.

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

“It’s mid-May,” he said, when “naturally there’s not a lot of flu.” Wolfe said he is not seeing an increase 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 were exposed to infected dairy cows for flu-like symptoms. Thirty-three people have been tested for the virus. So far, only one person – a dairy farm worker in Texas – has been diagnosed with bird flu linked to the dairy cow outbreak. He developed a serious case of conjunctivitis, or conjunctivitis, and recovered.