Highly pathogenic avian flu was detected in a backyard flock of birds in Franklin County last week, state officials said Thursday.

On Dec. 19, officials from the Vermont Agency of Agriculture, Food and Markets made a house call to a concerned animal owner whose two-dozen non-poultry birds had begun to die from an unknown illness. Two days later, while samples from the flock were being processed in a federal lab in Iowa, the agency culled the rest of the flock with the owner’s permission.

The owner and other individuals who had direct or indirect contact with the infected birds were being monitored by the Vermont Department of Health, according to the agency of ag. Officials did not identify the town in which the birds lived.

Though New England has so far not seen any documented cases of H5N1 bird flu, as the virus is also called, over 60 people have been infected across the country since the outbreak began in March 2024, according to the federal Center for Disease Control and Prevention. And while the virus officially remains a “low risk to human health,” according to the agency of ag, a growing chorus of health professionals continues to raise the alarm that a few quick mutations could change the picture drastically. So far, documented symptoms include conjunctivitis, fevers, body aches and nausea.

Last Wednesday, the CDC confirmed the “first severe case” of H5N1 in a human after a patient was hospitalized in Louisiana.

And over the past 30 years, roughly half of some 900 people around the world diagnosed with bird flu have died. The Franklin County case marks the fourth documented instance of H5N1 in a domestic flock in Vermont since 2022.

Avian flu has spread through just under 900 dairy herds across 16 states, according to the CDC, but agency of ag officials said Thursday that the case detected in Franklin County was not the same strain as what has hit dairy herds elsewhere.

State and federal officials urged animal owners to stay vigilant. Suggestions include reporting sick and dead birds and cattle, and reviewing biosecurity measures to protect herds and flocks.