As avian influenza rages through birds and dairy cattle across the United States, Georgia has become the latest state to detect the virus in a commercial poultry flock, and on Friday, it halted all poultry sales to mitigate further spread of the disease. Nationally, egg prices are soaring—if you can find them at all in your local grocery store.
The ongoing outbreak in animals has also led to at least 67 human cases of bird flu, with all but one causing mild illness. Earlier this month, a person in Louisiana died after being hospitalized with severe bird flu in December. It’s the country’s first recorded death attributed to H5N1.
The US has previously licensed three H5N1 vaccines for humans, but they’re not available commercially. The government has purchased millions of doses for the national stockpile in case they’re needed. But even as the outbreak spread, federal health officials under President Joe Biden were hesitant to deploy them. Experts say the decision comes down to risk, and currently, the risk of H5N1 remains low. Rolling out a vaccine to farm workers and others at higher risk of infection would be a more targeted tactic, but even that measure may be premature. Now, with a changeover in federal health leadership imminent as President Donald Trump begins his second term, the decision rests with the new administration.
“At the moment, from the point of view of severity and ease of transmission, it does not seem like an imperative to get a vaccine out to protect humans,” says William Schaffner, a physician and professor of preventive medicine at Vanderbilt University in Tennessee.
So far, no person-to-person spread of H5N1 has been identified, but health officials are monitoring the virus for any genetic changes that would make transmission among people more likely. Most bird flu infections are related to animal exposures. Of the 67 known human cases in the US, 40 have been linked to sick dairy cattle and 23 are associated with poultry farms and culling operations. In the other four cases, the exact source isn’t known.
In the US, human cases have been mild, with many of them causing only conjunctivitis. In some cases, people have had mild respiratory symptoms. Aside from the Louisiana patient, all the individuals who tested positive for H5N1 recovered quickly and never needed to be hospitalized. Historically though, H5N1 has been fatal in around 50 percent of cases. Since 2003, a total of 954 cases of human H5N1 have been reported to the World Health Organization, and about half of them died. Egypt, Indonesia, Vietnam, Cambodia, and China have reported the highest number of human bird flu deaths.
Those numbers come with a few caveats. For one, many of those deaths occurred in places where people live very close to the sick poultry. “In those circumstances, the thinking is that they likely got a very large dose of the virus,” Schaffner says.
Plus, the case fatality rate—the proportion of infected people who die from the disease—only takes into consideration known cases, and some cases of H5N1 are no doubt going undetected in part because bird flu symptoms are similar to other respiratory viruses. In the US, language barriers among farm workers, lack of testing, and a reluctance among workers to report that they’re sick are also factors. “We probably miss more cases than we detect, and we’re much more likely to detect a case that’s severe,” says Shira Doron, chief infection control officer for Tufts Medicine in Boston and hospital epidemiologist at Tufts Medical Center.
