A genetic analysis of samples from the patient in Louisiana recently hospitalized with the country\u2019s first severe case of H5N1 bird flu show the virus likely mutated in the patient to become potentially more transmissible to humans, but there\u2019s no evidence the virus has been passed to anyone else. <\/p>\n
The patient was likely infected after having contact with sick and dead birds in a backyard flock, the US Centers for Disease Control and Prevention said earlier this month. In an analysis Thursday, the agency said the mutations it identified in samples taken during the patient\u2019s hospitalization weren\u2019t found in the birds, suggesting they aren\u2019t in the virus widely circulating in wildlife. <\/p>\n
The mutations, similar to ones observed in a hospitalized patient in British Columbia, Canada, may make it easier for the virus to bind to cell receptors in humans\u2019 upper respiratory tracts, the agency said in its analysis. <\/p>\n
\u201cThe changes observed were likely generated by replication of this virus in the patient with advanced disease rather than primarily transmitted at the time of infection,\u201d the CDC said. \u201cAlthough concerning, and a reminder that A(H5N1) viruses can develop changes during the clinical course of a human infection, these changes would be more concerning if found in animal hosts or in early stages of infection\u2026 when these changes might be more likely to facilitate spread to close contacts.\u201d <\/p>\n
The agency emphasized the risk to the general public has not changed and remains low, but said the detection of the genetic mutations \u201cunderscores the importance of ongoing genomic surveillance in people and animals, containment of avian influenza A(H5) outbreaks in dairy cattle and poultry, and prevention measures among people with exposure to infected animals or environments.\u201d <\/p>\n
The analysis found no changes associated with markers that might mean antiviral drugs wouldn\u2019t work as well against the virus, the CDC added, and noted the samples are closely related to strains that could be used to make vaccines, if needed. <\/p>\n
The sequences also didn\u2019t show changes in genes associated with adaptation to mammals, the CDC found. The patient was infected with a strain known as D1.1 that\u2019s closely related to viruses circulating in wild birds and poultry in the U.S.; another strain known as B3.13 has been spreading widely in dairy cows and hasn\u2019t been found to cause severe disease in humans in the U.S. <\/p>\n
\u201cWhile this sounds like good news, the H5N1 situation remains grim,\u201d Dr. Angela Rasmussen, a virologist at the Vaccine and Infectious Disease Organization at the University of Saskatchewan in Canada, posted on Bluesky on Thursday. <\/p>\n
\u201cThere has been an explosion of human cases,\u201d she said. \u201cWe don\u2019t know what combination of mutations would lead to a pandemic H5N1 virus\u2026 but the more humans are infected, the more chances a pandemic virus will emerge.\u201d <\/p>\n
The CDC has confirmed 65 cases of H5N1 bird flu in humans in 2024. Of those, 39 were associated with dairy herds and 23 with poultry farms and culling operations. For two cases, the source of exposure is unknown. The severe case in the Louisiana is the only one associated with backyard flocks. <\/p>\n
Dr. Paul Offit, a vaccine scientist at Children\u2019s Hospital of Philadelphia, noted the CDC said the mutations \u201cmay\u201d enable to the virus to bind better to cell receptors in humans\u2019 upper respiratory tracts, not that they clearly do. <\/p>\n
\u201cAnd more importantly,\u201d Offit added, \u201cthere\u2019s not the clinical relevance that you see human-to-human spread.\u201d <\/p>\n<\/p>\n
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