Wastewater tests from the US show that the bird flu virus is limited to areas with farm animals

An extensive analysis of wastewater samples taken from May to July in the United States turned up traces of H5N1 bird flu, but only in areas populated by farm animals.

The bird flu virus is widespread among American poultry and herds of dairy cows, raising alarm bells that the virus could somehow mutate and spread between people.

The wastewater tests carried out between May 12 and July 13 are reassuring and suggest the virus is still targeting animals.

Nine of the 41 states where flu viruses were detected in wastewater showed locations with traces of the H5N1 virus in samples, the CDC said.

However, “among the nine states with H5 detections in wastewater, there were seven states with an HPAI A[H5N1]–infected herd reported during this period and one additional state with an infected herd reported before this period,” the agency said reported September 19 in his diary Weekly Morbidity and Mortality Report.

Those nine states are California, Colorado, Idaho, Iowa, Michigan, Minnesota, North Carolina, South Dakota and Texas.

So far, only 14 cases of human infection with H5N1 have been reported, typically causing mild illness, and almost all among people in close contact with infected animals, such as dairy workers.

In the new wastewater report, “two of these nine states [Colorado and Michigan] has reported confirmed human cases of HPAI A(H5N1) virus infection during this period,” said the team led by Souci Louis, an investigator with the CDC’s Epidemic Intelligence Service.

“Follow-up investigations in many of these states have likely identified animal-related sources, including sources associated with milk processing,” the team concluded.

However, the researchers added that wastewater testing is not yet foolproof as to the source of the virus, because “although influenza viruses can be detected in wastewater, current techniques cannot distinguish between human and animal sources.”

The same team also looked for signs of influenza A viruses as a whole (of which H5N1 is a subtype). Influenza A viruses are linked to seasonal flu.

Report shows ‘eleven locations in four states’ during early summer [California, Illinois, Kansas and Oregon] reported high levels of influenza A virus,” indicating that influenza was regularly passed between people there.

“None of these four states reported human H5 flu [bird flu] There have also been no confirmed cases reported in herds of livestock or poultry in their sewage sheds or provinces during this period,” Louis’ team noted.

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