An ongoing outbreak of a deadly strain of bird flu has now killed more birds than any past outbreak in US history.
The virus, known as highly pathogenic bird flu, has killed 50.54 million domestic birds in the country this year, according to Agriculture Ministry data reported by Reuters on Thursday. This figure represents birds such as chickens, ducks and turkeys from commercial poultry farms, backyard flocks and facilities such as petting zoos.
The tally tops the previous record of 50.5 million dead birds in a 2015 outbreak, according to Reuters.
Separately, USDA data shows at least 3,700 confirmed cases in wild birds.
On farms, some birds die directly from the flu, while in other cases farmers kill their entire flock to prevent the virus from spreading after a bird tests positive. These farmers have sometimes been condemned by animal welfare advocates for using a slaughter method known as “shutdown plus ventilation”, which involves sealing the airways of a barn and injecting heat to kill animals.
The virus has been raging in Europe and North America since 2021. Various wild birds have been affected around the world, including bald eagles, vultures and seabirds. This month, Peru reported its first apparent outbreak of highly pathogenic bird flu after 200 dead pelicans were found on a beach.
The migration of infected wild birds has been a major cause of spread. Health and wildlife officials are urging anyone who keeps domestic birds to avoid contact with their wild counterparts.
While health experts don’t generally consider HPAI a major risk to mammals, a black bear cub in Alaska was euthanized earlier this month after contracting the virus. Wildlife veterinarian Dr Kimberlee Beckmen told the Juneau Empire newspaper that the young cub had a weakened immune system.
Over the summer, bird flu also spread among seals in Maine, which the National Oceanic and Atmospheric Administration says contributed to an unusually high number of seal deaths.
The Centers for Disease Control and Prevention say the risk “to the general public” from the bird flu outbreak is low. However, the agency recommends precautions such as wearing personal protective equipment and thorough hand washing for people who have prolonged contact with birds that may be infected.
In April, a Colorado prisoner working on a commercial farm became the first person in the United States to test positive for the new strain, despite being largely asymptomatic.