Throughout 2024, the US recorded dozens of human cases of H5N1 or bird flu, all of them mild, so far. The Centers for Disease Control and Prevention (CDC) confirmed on Wednesday, December 18, that a patient from Louisiana was hospitalized with a severe case of the virus, being the first severe case in the United States.
The virus has harmed flocks of poultry and wild birds across the country and infected more than 800 dairy herds in 16 states. Infected animals transmit the virus to people who come into contact with them. Since April, 61 human cases of bird flu have been reported in eight states: of those, 37 were exposed to sick or infected dairy cows, while 21 were employed in poultry farms and slaughter operations. In these cases, people developed conjunctivitis and mild respiratory symptoms, and were able to recover completely.
An unusual infection
In other countries, bird flu is associated with severe illness, including outbreaks that resulted in death in up to 50% of cases. Between 2003 and 2023, of the 878 people who tested positive for the virus, 458 died. An investigation by the Louisiana Department of Health and the CDC determined that the hospitalized patient, a resident of southwest Louisiana, was exposed to sick and dead birds in flocks in his backyard. This is the first case in the entire US related to exposure to a backyard flock, and not a commercial farm.
“Although the origin of this infection in Louisiana is under investigation, the patient Louisiana reported is believed to have been exposed to sick or dead birds on their property,” said Demetre Daskalakis, director of the CDC’s National Center for Immunization and Respiratory Diseases. , during a press conference held on Wednesday. No further details are available regarding the source of exposure or the patient’s condition.
In late August in Missouri, a person with bird flu was hospitalized, but CDC officials say it was due to “underlying medical conditions.” The patient did not have respiratory symptoms nor was he seriously ill from the infection: “In the Missouri case, we don’t really have the same type of data to support that it was related to a flu infection,” Daskalakis emphasizes.
There are genetic similarities between the Louisiana patient’s virus and that of a Canadian teenager hospitalized with H5N1. Scientists classify the Louisiana virus as type D1.1, the same one found in the Canadian patient and in another case from Washington state. This variant has also been detected in wild and poultry birds in the United States. It is different from type B3.13, which has been detected in dairy cows, in some outbreaks in poultry, and in sporadic human cases in several states. CDC scientists working on additional genomic sequencing of Louisiana patient’s viral sample; This could identify potentially worrying changes in the virus that would indicate an increased ability to infect humans or transmit from person to person.
So far, no human-to-human transmission of H5N1 bird flu has been detected. The CDC says the immediate risk to public health remains low, but that people exposed to infected animals through work or recreation are at greater risk of contracting the virus: “This means backyard bird owners, hunters, and others Bird enthusiasts should also take precautions,” the agency clarifies in a statement.
Article originally published in WIRED. Adapted by Alondra Flores.
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