The United States has recorded its first fatal case of H5N1 bird flu in a Louisiana person who contracted the virus from infected chickens and wild birds in a backyard flock. The death was reported Monday by the Louisiana Department of Health.
The unidentified individual was described as being over 65 years old and reportedly had underlying medical conditions. It is not clear what those circumstances were and whether they put the person at increased risk of developing a serious flu infection.
The Centers for Disease Control and Prevention said in a statement that the event, while tragic, does not change its position on the current risk of the virus.
“CDC has carefully reviewed the available information about the individual who died in Louisiana and continues to assess that the risk to the general public remains low,” the CDC said in a statement.
Flu experts warned that while this was the first death from H5N1 in the country, more are likely to follow.
“I hesitate to make too many predictions about this virus, but I feel very confident in predicting that we will see more fatal cases if the H5 virus continues to circulate among birds and dairy cattle, which seems likely,” said Richard Webby, a flu priest. virologist who directs the World Health Organization Collaborating Center for Studies on the Ecology of Influenza in Animals, located at St. Jude Children’s Research Hospital in Memphis, Tennessee.
“The intrinsic ability of the current group of H5 viruses to cause disease in many species is virtually unparalleled in the world of influenza viruses. So even though fatal infections still represent a small percentage of human infections, tragically, we may not have seen the last of it.”
Angela Rasmussen agreed, suggesting it was only a matter of time before the country saw a fatal case. “I was kind of expecting something like this to happen,” said Rasmussen, a virologist who studies emerging infectious diseases at the Vaccine and Infectious Disease Organization at the University of Saskatchewan in Saskatoon, Canada.
While the H5N1 virus has claimed that more than 450 lives worldwide This is the first death from the virus in North America since 2003. The US has recorded 67 human cases of H5N1, all but one in 2024. All other cases had only mild symptoms.
An analysis of H5N1 cases in the United States published last week in the New England Journal of Medicine noted that there have been 11 human infections in five other countries since 2022, with the version of the virus currently circulating among dairy cattle in parts of the US, clade 2.3.4.4b. Of those, seven people had asymptomatic infection, four had severe or critical illness, one of which was fatal. The fatal case occurred in China in 2022.
The mildness of the preponderance of cases in the US has puzzled scientists who have been tracking H5N1 for years. Some are concerned that there is a perception that this version of the virus is in fact harmless and mainly causes conjunctivitis (pink eye) in infected people.
Rasmussen has cautioned against this view, suggesting that the relative lack of serious infections may be due to who gets infected – especially young, healthy farm workers – and how they get infected. Their illnesses may not tell us how the virus would behave in people who are more vulnerable to severe flu illnesses, she said.
“I didn’t think it was possible to actually have an H5N1 flu virus … which would mysteriously cause only mild illness in anyone infected with it,” Rasmussen said. “And to me, that’s the great benefit of the Louisiana patient: these viruses can cause serious illness. Maybe not at the same frequency as we have historically thought about H5N1, but they are certainly capable.”
Michael Osterholm, director of the University of Minnesota’s Center for Infectious Disease Research and Policy, was more cautious in his assessment of the Louisiana patient’s death, pointing out that it has long been known that this virus will kill some people. dead who become infected. infected with it. What he is looking for is any indication that the virus is adapting to spread easily from person to person, a prerequisite for the onset of a new pandemic.
“We must always take into account all flu cases and what they can teach us about what is happening. We also have to be very careful not to over-interpret what one case means,” Osterholm said.
Analysis of virus samples taken from the Louisiana individual showed that the virus had developed some mutations that are believed to increase its ability to attach to cells in the human upper respiratory tract. These changes were not seen among viruses from the birds in the person’s backyard flock, a fact that the Centers for Disease Control and Prevention says likely means they developed in the individual during the course of the infection.
Similar mutations were found in virus samples from a teenager in British Columbia, Canada, who also became seriously ill with H5N1. The 13 year old girl was in intensive care for several weeks, but is now recovering.
The Louisiana Department of Health statement said no new cases have been discovered among the contacts of the deceased person. Similarly, health authorities in British Columbia could find no evidence that the infected girl had transmitted the virus to anyone else.
H5N1 has long been at or near the top of the list of viruses on pandemic planners’ minds. Infections in wild birds have spread the virus around the world, and recent versions of the virus have shown a disturbing ability to infect multiple species of mammals, including dairy cows.
The outbreak in cows, first detected in late March, has spread to more than 900 herds in 16 states. Forty of the 66 human cases detected in 2024 were among farm workers exposed to infected cows.