BOSTON — The circulating bird flu has become “widespread” in the Bay State, as officials believe the virus has killed 500 to 1,000 wild birds across the region.

And the total number of dead birds is likely “much higher than that,” according to a MassWildlife scientist on Wednesday, noting that many cases do not get reported by the public.

“Surveillance testing of individual dead birds indicates the virus is widespread in the state among our wild water birds,” said Andrew Vitz, state ornithologist at MassWildlife.

State environmental and health officials are reporting that the Highly Pathogenic Avian Influenza H5N1 virus is suspected to be the cause of death in both wild and domestic birds in several Massachusetts communities.

MassWildlife, the Department of Agricultural Resources, and the Department of Public Health are urging residents to not handle birds or other animals that are dead or appear sick.

Although the virus is spreading among birds, the risk of human infection is low and there have been no confirmed cases in the Bay State.

“This is an animal virus right now,” said State Epidemiologist Catherine Brown. “While it can occasionally infect humans, it is not mutated in a way where it can infect people easily.”

People who have direct contact with animals infected with HPAI are the most at risk of becoming infected.

The virus arrived in North America in late 2021, and there have been periodic outbreaks since then, primarily around coastal areas.

Vitz called the recent jump in cases “our largest outbreak in terms of the impacts of the number of individual birds and the geographic distribution in the state.”

The current cases are primarily located in the Boston-area to southeast Massachusetts, while lower cases have been reported in central and western Mass.

Both wild and domestic birds can become infected with the virus.

“Raptors, waterfowl and other aquatic birds are most at risk for infection, although any bird species should be considered susceptible to the virus,” Vitz said.

Wild mammals, especially those that scavenge on wild birds like foxes, can also become infected.

“While human infections are rare, we urge the public to strictly avoid any contact with wildlife, especially any sick or dead birds or other animals,” Vitz said.

Dogs should be leashed and kept away from wildlife, and cats are highly susceptible to the virus and should be kept indoors.

With the rising positive cases in wild birds, it’s “crucial” for poultry owners to keep their flocks away from wild birds, said Ashley Randle, commissioner of the Massachusetts Department of Agricultural Resources.

Randle advised poultry owners to keep their flocks inside, away from the wild bird population.

The public is being urged to report observations to MassWildlife of sick or dead wild birds if five or more birds are found at a single location. People can report the sick or dead birds at mass.gov/reportbirds.

Also, people should report sick or dead poultry or other domestic birds by calling MDAR’s Division of Animal Health at 617-626-1795 or through mass.gov/reportpoultry.

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