United States has recorded dozens of cases of human bird flu this year, all subtle – so far.
Centers for Disease Control and Prevention confirmed on Wednesday that a patient in Louisiana was hospitalized with a severe case of bird flu caused by the H5N1 virus. This is the first case of severe illness linked to the virus in the US.
The virus has decimated poultry flocks 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. The total has been recorded in the US since April There have been 61 human cases of bird flu reported in eight states. Of these, 37 had contact with ill or infected dairy cows, and 21 had contact with poultry farms and slaughterhouses. In such cases, patients developed conjunctivitis and subtle respiratory symptoms and subsequently made a full recovery.
The severe case is significant because bird flu has already been linked to stern illnesses in other countries, including epidemics that ended in death in 50% of cases. Between 2003 and 2023, of the 878 people who tested positive for the virus, 458 deaths were reported.
An investigation by the Louisiana Department of Health and CDC determined that the hospitalized patient, a southwest Louisiana resident, had contact with ill and dead birds in backyard flocks. This is the first case of H5N1 bird flu in the U.S. linked to exposure to a domestic rather than a commercial flock.
“While the investigation into the source of this infection in Louisiana is ongoing, the patient reported by Louisiana is believed to have had contact with sick or dead birds on his property,” Demetre Daskalakis, director of the CDC’s National Center for Immunization and Respiratory Diseases, said during a Wednesday briefing press release. No other details are available about the source of exposure or the patient’s condition.
A person with bird flu in Missouri was hospitalized in behind schedule August, but CDC officials say it was due to underlying health conditions. The patient had no respiratory symptoms and was not seriously ill due to infection. “In the case of Missouri, we don’t really have the same type of data to support that it was related to influenza infection,” Daskalakis said.
There are genetic similarities between the virus from the Louisiana patient and the virus from a Canadian teenager who was hospitalized with H5N1. Scientists have classified the virus found in Louisiana as type D1.1, the same type found in a patient in Canada and another case in Washington state. The variant has also been detected in wild birds and poultry in the US.
This is different from type B3.13, which has been detected in dairy cows, in some poultry outbreaks and in sporadic cases in humans in many states. CDC scientists are conducting additional genome sequencing of a virus sample from a patient in Louisiana. Genome sequencing can identify potentially concerning changes in the virus that signal an increased ability to infect people or spread from person to person.
So far, no human-to-human transmission of the H5N1 avian influenza virus has been detected. The CDC says the immediate risk to public health remains low, but people who come into contact with infected animals at work or for recreation are at greater risk of contracting the virus. “This means that backyard flock owners, hunters and other bird lovers should also take precautions,” the agency said in a statement.