There have been no confirmed human cases of bird flu in Massachusetts, but state officials this week issued guidance on how to avoid infection.
In other parts of the United States, there have been 67 cases and one death associated with infection of the highly pathogenic avian influenza (HPAI).
State epidemiologist Catherine Brown, with the Massachusetts Department of Public Health, said human infections are rare.
"This is an animal virus right now. While it can occasionally infect humans, it is not mutated in a way where it can infect people easily," she said.
Brown is also the state public health veterinarian.
Ashley Randle, commissioner of the Massachusetts Department of Agricultural Resources, said the state has tested dairy herds on licensed farms since August and has had "100% negative results" for avian flu.
Randle thanked dairy farmers "for adhering to best practices to ensure that we have a safe milk supply for all of our consumers."
Randle advised poultry farmers and people with backyard flocks to keep birds inside, even cage-free birds.
"It's crucial for poultry owners to keep their flocks away from wild birds, especially waterfowl," Randle said.
So far, wild birds — mostly swans and geese — have been infected in Massachusetts.
"Cases are primarily located from Greater Boston through the southeast portion of the state, with lower numbers of cases in central Massachusetts and the Connecticut River Valley," said ornithologist Andrew Vitz with the Division of Fisheries and Wildlife.
Vitz said the agency has a couple of "preliminary positive" cases of infected wild birds in central and western Massachusetts, but they haven't been confirmed yet.
Last week, the state confirmed that wild birds on the UMass Amherst campus, found dead, had tested positive. Vitz said the state is no longer getting reports of sick or dead birds on the campus.
Vitz advised people and their pets avoid contact with dead, wild birds, and with wildlife in general.
"Dogs and other pets should be leashed and kept away from wildlife. Cats are highly susceptible and should be kept indoors," he said.
Vitz said some birds infected with the virus may not show any signs of illness, but "they can transmit the virus through droppings and other bodily fluids. Wild mammals, especially those that scavenge on wild birds, such as foxes, can also become infected."
Raptors, including bald eagles, are also at risk because they prey on carcasses of dead birds.
Vitz noted the state has a healthy population of bald eagles.
"We are hoping that those robust populations will be able to deal with upticks in the virus that we're seeing now," he said.