(CNN) — A genetic evaluation of samples from the affected person in Louisiana not too long ago hospitalized with the nation’s first extreme case of H5N1 hen flu present the virus doubtless mutated within the affected person to change into doubtlessly extra transmissible to people, however there’s no proof the virus has been handed to anybody else.
The affected person was doubtless contaminated after having contact with sick and lifeless birds in a yard flock, the US Facilities for Illness Management and Prevention stated earlier this month. In an evaluation Thursday, the company stated the mutations it recognized in samples taken throughout the affected person’s hospitalization weren’t discovered within the birds, suggesting they aren’t within the virus broadly circulating in wildlife.
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The mutations, much like ones noticed in a hospitalized affected person in British Columbia, Canada, could make it simpler for the virus to bind to cell receptors in people’ higher respiratory tracts, the company stated in its evaluation.
“The 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,” the CDC stated. “Although 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… when these changes might be more likely to facilitate spread to close contacts.”
The company emphasised the chance to most people has not modified and stays low, however stated the detection of the genetic mutations “underscores 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.”
The evaluation discovered no modifications related to markers which may imply antiviral medicine wouldn’t work as nicely towards the virus, the CDC added, and famous the samples are carefully associated to strains that might be used to make vaccines, if wanted.
The sequences additionally didn’t present modifications in genes related to adaptation to mammals, the CDC discovered. The affected person was contaminated with a pressure often known as D1.1 that’s carefully associated to viruses circulating in wild birds and poultry within the U.S.; one other pressure often known as B3.13 has been spreading broadly in dairy cows and hasn’t been discovered to trigger extreme illness in people within the U.S.
“While this sounds like good news, the H5N1 situation remains grim,” Dr. Angela Rasmussen, a virologist on the Vaccine and Infectious Illness Group on the College of Saskatchewan in Canada, posted on Bluesky on Thursday.
“There has been an explosion of human cases,” she stated. “We don’t know what combination of mutations would lead to a pandemic H5N1 virus… but the more humans are infected, the more chances a pandemic virus will emerge.”
The CDC has confirmed 65 instances of H5N1 hen flu in people in 2024. Of these, 39 have been related to dairy herds and 23 with poultry farms and culling operations. For 2 instances, the supply of publicity is unknown. The extreme case within the Louisiana is the one one related to yard flocks.
Dr. Paul Offit, a vaccine scientist at Kids’s Hospital of Philadelphia, famous the CDC stated the mutations “may” allow to the virus to bind higher to cell receptors in people’ higher respiratory tracts, not that they clearly do.
“I’d like to see clear evidence… that it binds well,” Offit instructed CNN Friday. “That hasn’t happened yet.”
“And more importantly,” Offit added, “there’s not the clinical relevance that you see human-to-human spread.”
The-CNN-Wire
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