This is the 14th human case of bird flu reported this year in the United States and the first without a known occupational exposure to infected animals.
By Lena H. Sun
September 6, 2024
An individual in Missouri has contracted bird flu, the first human infection unconnected to farm work in an outbreak detected in the spring when the disease was discovered among dairy cows.
The H5N1 avian influenza has spread from cattle to poultry, cats and other animals across the country.
The Missouri individual is the 14th human case of bird flu reported this year in the United States and the first without a known occupational exposure to infected animals, according to the Centers for Disease Control and Prevention. It is also the first time the national flu surveillance system has detected a case of H5 bird flu, the CDC said.
The person was hospitalized Aug. 22, and routine flu testing showed the person had a type of novel nonhuman influenza virus that is different from seasonal human influenza virus. Subsequent testing at the Missouri public health lab and the CDC confirmed the virus as avian flu.
The individual, who has underlying medical conditions that could have made the person more susceptible to respiratory illnesses, was treated with influenza antiviral medication and has recovered. State officials said no transmission among close contacts or others has been identified. Health officials are not providing additional patient information to protect the person’s privacy.
“I’m really glad we have a robust flu system that picked this up, but [it] just begs the question: How many cases have we missed?” said Katelyn Jetelina, an epidemiologist who writes a weekly infectious-diseases newsletter and has closely tracked the avian flu outbreak. “In these situations, we can’t fly blind. If we have a full picture, we can better act, communicate and prevent.”
More than five months into the outbreak, many unanswered questions remain. Public health experts and groups representing farmworkers say the actual number of people infected is certain to be higher because of insufficient testing of people, cows and raw milk.
The outbreak of H5N1 has infected nearly 200 dairy herds in 14 states, according to the U.S. Department of Agriculture; Missouri is not among them. But outbreaks of H5 have been reported in the state’s commercial and backyard poultry flocks this year. H5N1 bird flu has been detected in wild birds in Missouri in the past, according to the CDC.
Federal officials this week added California, the country’s largest milk producer, to the list of states with infected cattle after three dairy herds tested positive for bird flu.
The CDC said its assessment of the risk to the general public remains low, but findings from its investigation into how the Missouri individual without obvious animal exposure contracted the virus will determine whether the agency needs to change its guidance.
Preliminary genetic analysis of the virus shows no evidence of changes that would make it more easily transmitted to humans, a federal health official said, speaking on the condition of anonymity because the investigation is ongoing.
“We haven’t seen evidence of any other type of respiratory illness” in the area where the individual lives, the official said.
The bird flu investigations typically involve detailed questionnaires about a person’s exposures to raw milk products, visits to state fairs or animal exhibits or zoos, and exposure to birds and bird feces, the official said.
CDC officials have stressed repeatedly that its national flu surveillance system would detect unusual influenza activity in people, including cases of H5N1. Since Feb. 25, more than 46,000 flu specimens have been tested for novel influenza viruses, including H5, according to the agency.
Missouri health officials said they are closely monitoring surveillance data. There has been no sign of unusual influenza activity among people such as upticks in emergency room visits or laboratory detection, according to a statement from Missouri’s Department of Health and Senior Services.
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By Lena H. SunLena H. Sun is a national reporter for The Washington Post covering health with a special focus on public health and infectious disease. A longtime reporter at The Post, she has covered the Metro transit system, immigration, education and was a Beijing bureau chief. follow on X @bylenasun
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