First Human Bird Flu Death in U.S. Reported—How Worried Should We Be? todayheadline

What Does First U.S Bird Flu Death Tell Experts about Disease Severity?

By Tanya Lewis edited by Dean Visser

The Louisiana Department of Health recently reported the first U.S. death from H5N1 avian influenza: this individual was a patient who became severely ill and was hospitalized after having contact with both backyard poultry and wild birds. The department didn’t identify the deceased but said the person was older than age 65 and had underlying health conditions.

A total of 66 confirmed human cases of bird flu have been reported in the U.S. since the beginning of 2024. Most have been very mild and have occurred in people who work with dairy cattle or poultry. The scant handful of severe cases that have occurred throughout North America during that time have included one person in Missouri who was hospitalized and tested positive for the H5N1 virus and a 13-year-old in British Columbia who also had obesity and asthma and had been listed as in critical condition, according to a recent study published in the New England Journal of Medicine. In previous international outbreaks in humans, the virus has had a reported mortality rate of more than 50 percent, though that is likely an overestimate because not all cases are caught.

The death in Louisiana and hospitalizations in Missouri and British Columbia are concerning, but they have not changed the U.S. Centers for Disease Control and Prevention’s assessment that the risk to the general public from H5N1 remains low.

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“We have to put H5N1 deaths in perspective. This has been a horrible disease for well over 27 years in humans,” says Michael Osterholm, chair of public health and director of the Center for Infectious Disease Research and Policy at the University of Minnesota. Yet “the virus activity we’re seeing now, in terms of cases, has been largely a very mild illness,” Osterholm adds. “And while there have been two severe cases, both of these individuals also had underlying health conditions that would predispose them to severe disease.”

In comparison, he notes that there have been more than 2,700 deaths from seasonal flu in the U.S. so far this fall and winter alone. When it comes to bird flu, “we seem to live in two separate universes: one where we have a state like California, which has just declared a state of emergency over bird flu, and then you have the CDC saying it’s low-risk—and they’re both right,” he says. Osterholm likens the current situation to walking safely along a long, flat field and then suddenly coming upon the edge of a cliff with a mile-high drop. Once one gets past that edge, “that’s what a pandemic is,” he says. So it’s accurate to say the risk is low right now, he adds—but that could change “in a heartbeat.”

So far there have not been any reports of human-to-human spread of H5N1 in the U.S. That’s not a reason to be complacent, however. The more people are exposed to or infected with H5N1, the higher the chances are that the virus will mutate and mix with seasonal flu viruses, possibly making it easier to spread between people.

The individuals in the Louisiana and British Columbia cases were both infected with viruses related to the D1.1 bird flu genotype that is currently circulating in wild birds and poultry—not the B3.13 strain that is circulating in cattle. It’s too soon to draw conclusions about whether the avian strain is more virulent, however, Osterholm says.

Public health experts say one thing is clear: people who work with or have contact with wild birds, poultry or cattle should take precautions. More than two thirds of California’s dairy herds have been infected with H5N1 in the past year, and human cases may be going uncounted (especially if they are mild). Dairy workers are at risk from the milking process, during which milk with high levels of virus could splash into their eyes. Poultry workers have been infected while culling sick birds. Several domestic cats have been infected after drinking raw milk or consuming raw meat. Fortunately, pasteurization or cooking to the appropriate temperature kills the virus.

It’s too soon to tell whether H5N1 will develop into a pandemic. “I’ve been worried about a flu pandemic dating back to the last [flu pandemic], and that includes time during COVID,” Osterholm says. Worldwide, vaccine makers have capacity to make enough bird flu vaccine to inoculate fewer than two billion people (about 25 percent of the world’s population) in the first year after an outbreak. “We’re extremely vulnerable right now, on a global basis, to a flu pandemic,” Osterholm says. “So, yeah, I worry about that every day, whether it’s H5N1 or H2N2 or some other virus that emerges out of the flu world.”