Louisiana bird flu patient virus may increase transmissibility to humans

(CNN) – A genetic analysis of samples from patient in Louisiana recently hospitalized with the first severe case of H5N1 bird flu in the country, it shows that the virus has undergone mutations in the patient to become potentially more transmissible to humans, but there is no evidence that the virus has been transmitted to anyone else.

The patient was likely infected after coming into contact with sick and dead birds from a backyard flock, US Centers for Disease Control and Prevention saidat the beginning of this month. Ino analysis On Thursday, the agency said the mutations it identified in samples taken during the patient’s hospitalization were not found in the birds, suggesting they are not in the virus that circulates widely in wildlife.

The mutations, similar to those observed in a inpatient of British Columbia, Canada, may facilitate the binding of the virus to cell receptors in the upper respiratory tract of humans, the agency said in its analysis.

“The observed changes were likely generated by the replication of this virus in the patient with advanced disease, rather than primarily transmitted at the time of infection,” the CDC said. “While of concern and the reminder that A(H5N1) viruses can develop changes during the clinical course of a human infection, these changes would be more concerning if they are found in animal hosts or in the early stages of infection … when these changes could be more likely. to facilitate spread to close contacts.”

The agency emphasized that the risk to the general public has not changed and remains low, but said the detection of genetic mutations “underscores the importance of continued genomic surveillance in humans and animals, control of avian influenza A(H5) outbreaks in dairy cattle and poultry yard and preventive measures among people exposed to infected animals or environments.”

The analysis found no changes associated with the markers that could mean antiviral drugs would not work as well against the virus, the CDC added, noting that the samples are closely related to strains that could be used to make vaccines, if is necessary.

The sequences also showed no changes in genes associated with adaptation in mammals, the CDC found. The patient was infected with a strain known as D1.1, which is closely related to viruses circulating in wild birds and poultry in the US; another strain known as B3.13 has spread widely in dairy cows and has not been found to cause severe disease in humans in the US

“While this sounds like good news, the H5N1 situation remains grim,” Dr. Angela Rasmussenvirologist at the Vaccine and Infectious Diseases Organization at the University of Saskatchewan in Canada, POSTEDon Bluesky Thursday.

“There has been an explosion of human cases,” she said. “We don’t know what combination of mutations would lead to a pandemic H5N1 virus … but the more people infected, the more likely a pandemic virus will emerge.”

CDC has confirmed65 human cases of H5N1 avian influenza in 2024. Of these, 39 were associated with dairy herds and 23 with poultry farms and slaughter operations. In two cases, the source of exposure is unknown. The severe case in Louisiana is the only one associated with backyard herds.

Dr. Paul Offita vaccine scientist at the Children’s Hospital of Philadelphia, noted that the CDC said the mutations “may” allow the virus to bind better to cell receptors in people’s upper respiratory tract, not that they clearly do.

“I would like to see clear evidence … that they bond well,” Offit told CNN on Friday. “That hasn’t happened yet.”

“More importantly,” Offit added, “there’s not the clinical relevance that you see spreading from person to person.”