Understanding bird flu and the health risk for humans

Bird flu or avian influenza, widespread in wild birds across the world, is causing outbreaks in millions of American poultry and hundreds of dairy cattle herds. It has also been linked to 61 human cases confirmed in the United States this year. Most involve dairy or poultry workers, according to the Centers for Disease Control and Prevention.

The CDC has said that public health risk from this influenza strain, known formally as H5N1, is low. But in Louisiana this month, in the first instance of severe illness linked to the virus in the United States, a person was hospitalized with a severe case of bird flu. California this week declared an emergency over the flu’s spread in cattle there.

What’s the risk to human health?

Avian influenza virus infections in humans may cause mild to severe upper respiratory tract infections and can be fatal, according to the World Health Organization. Conjunctivitis, gastrointestinal symptoms, encephalitis and encephalopathy have also been reported.

Human infection with bird viruses is rare and infectious disease experts told Newsday they generally agreed with the CDC’s risk assessment. One reason is that there is currently no evidence of human-to-human transmission of the virus, said Dr. Bruce Farber, Northwell Health’s chief epidemiologist. "Day to day, people do not have to worry about bird flu," he said. Risk of animal-to-human transmission for people who do work closely with sick, potentially sick or dead animals can also be reduced by wearing protective gear.

But there are reasons for concern. Of 878 confirmed cases of human H5N1 infection reported to the World Health Organization from 2003 to 2023, 458 resulted in death. That number is tiny compared to the toll from run-of-the-mill seasonal flu, but the fatality rate is much higher.

If the avian influenza virus currently circulating mutates to become transmissible person-to-person, it could spread through the general population, Farber said. "Whether that will occur or not is clearly up in the air," he said.

H5N1’s capacity for spillover to new hosts is troubling, said Columbia University epidemiologist Stephen Morse. "Over the years, we’ve seen other species become infected and these last couple of years in particular we’ve seen a lot of different mammal species, altogether about 48," including not just cattle but pigs. "This is a special concern because many pandemics seem to have come through pigs as a mixing vessel" for hybrid human-animal viruses.

Because bird flu has thus far little circulation in the human general population, "no one is really immune to it, and that’s what leads to epidemics," said Dr. Sharon Nachman, chief of pediatric infectious diseases at Stony Brook Children’s Hospital. For the moment, though, seasonal flu is a much more pressing concern, she said. As for bird flu, "It’s reasonable to be concerned, but not to hide in your house."

What should the general public do to protect themselves?

The CDC recommends that people avoid direct contact with wild birds or other animals infected with or suspected to be infected with bird flu. It is safe to eat properly handled and cooked poultry in the U.S., and cooking poultry or eggs to an internal temperature of 165 degrees will kill bacteria and viruses, including bird flu. Pasteurized milk is safe to drink but people should avoid unpasteurized or raw milk.

Experts also recommend getting a seasonal flu shot. While it won’t protect against bird flu, it may reduce the chance of human influenza strains mixing with avian influenza viruses, in turn reducing the risk of a virus emerging that is likely to spread from human to human, according to the state Department of Health.

What’s the situation on Long Island and across New York?

The state’s Department of Health is "using all the tools at its disposal to monitor for avian influenza in humans and is prepared for widespread testing should the need arise," Erin Clary, a spokeswoman for the agency, wrote in an email.

While Clary said there are currently no human or livestock cases of avian influenza in New York, there have been 27 animal cases statewide linked to the latest outbreak, including four in Suffolk County, involving wild birds or backyard flocks, according to the state Department of Agriculture and Markets.

A spokeswoman for the agency, Hanna Birkhead, said its staffers have been monitoring state poultry farms and backyard flocks since 2022, enforcing regulations covering the import of animals and testing requirements, as well as holding regular information sessions for the industry.

Across New York, according to the United States Department of Agriculture, one commercial flock and 25 backyard flocks have been affected by the current outbreak, totaling 25,872 poultry, but no infections in the last month.

Rob Carpenter, administrative director for the Long Island Farm Bureau, said the handful of professional poultry operations on Long Island already take safety measures that include hygiene for workers and segregating their flocks from the wild bird population and from other flocks to prevent any possible spread.

But there are a "tremendous number of backyard enthusiasts" keeping a few birds for eggs. "The major concern is that [they] might not be aware of the risk," he said.

Across New York, according to the United States Department of Agriculture, one commercial flock and 25 backyard flocks have been affected by the current outbreak, totaling 25,872 poultry, but no infections in the last month.