An extensive look at wastewater samples taken across the United States from May to July found traces of the H5N1 bird flu popping up -- but only in areas populated by farm animals.

Researchers in Texas detected H5N1 in wastewater from 10 cities, but the risk to humans is currently low. Ongoing surveillance is critical to monitor any potential changes in the virus that could increase its threat to public health.

Bird flu typically spreads among birds, but there have been recent outbreaks among cattle in the U.S., and one Texas man contracted the virus from sick cows. Here’s why so many experts are worried about a possible new pandemic.

Hanson and Tisza noted that they track many other viruses, and have seen the summer COVID surge in their surveillance, as well as the uptick in parvovirus B19 that was the subject of a CDC-issued HAN advisory earlier this summer.

"The widespread detection of influenza A (H5N1) virus in wastewater from 10 U.S. cities is troubling," the authors concluded. "Although the exact origin of the signal is currently unknown, the lack of clinical burden along with genomic information suggests multiple animal sources."