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.

With cold and flu season approaching, it’s worth knowing about another virus out there—albeit extremely rare: bird flu. Like the regular flu, bird flu virus symptoms include fever, cough and a sore throat.

On Monday state officials announced they had completed testing on all 95 licensed farms in Massachusetts that have dairy herds, the first state in the nation to do so. The results were “100 percent negative.” The testing program is likely to be repeated on a regular basis going forward, and could serve as a national model.

Several labs will work with federal health authorities to develop a test for avian influenza, as the number of human cases rise across the country.

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.