WASHINGTON
\nThe ongoing spread of bird flu in the United States has alarmed experts \u2014 not just because of human cases causing severe illness, but also due to troubling new instances of infections in cats.
\nA sample of the virus found in a critically ill patient in the United States has shown signs of mutating to better suit human airways, although there is no indication it has spread beyond that individual, authorities report.
\nEarlier this month, officials announced that an elderly Louisiana patient was in \u201ccritical condition\u201d with a severe H5N1 infection.
\nAn analysis posted by the Centers for Disease Control and Prevention (CDC) Thursday revealed that a small percentage of the virus in the patient\u2019s throat carried genetic changes that could increase the virus\u2019s ability to bind to certain cell receptors found in the human upper respiratory tract.
\nImportantly, the CDC noted that these changes have not been detected in birds \u2014 including in the backyard poultry flock believed to have been the source of the patient\u2019s initial infection.
\nInstead, the agency said the mutations were \u201clikely generated by replication of this virus in the patient with advanced disease,\u201d emphasizing that no transmission of the mutated strain to other humans had been identified.
\nSeveral experts contacted by AFP cautioned that it was too early to determine whether these changes would make the virus more transmissible or more severe in people.
\nAngela Rasmussen, a virologist at the University of Saskatchewan in Canada, explained that while the mutation might help the virus enter cells more easily, additional evidence \u2014 such as animal testing \u2014 would be needed to confirm any effect on transmissibility.
\nMoreover, similar mutations have occurred in previous critically ill patients without leading to broader outbreaks.
\n\u201cIt\u2019s good to know we should be looking out for this,\u201d Rasmussen said, \u201cbut it doesn\u2019t actually tell us, \u2018Oh, we\u2019re this much closer to a pandemic now.\u2019\u201d
\nThijs Kuiken of Erasmus University Medical Center in the Netherlands agreed.
\n\u201cEfficient attachment to human upper respiratory tract cells is necessary, but not sufficient, for more efficient transmissibility between people,\u201d he said, adding that the process is just one among several steps required for successful viral replication.
\nRather than intensifying disease, Kuiken pointed out, such adaptations might actually result in milder infections by favoring cells in the upper respiratory tract \u2014 causing symptoms like a runny nose or sore throat \u2014 rather than affecting the lower respiratory tract, which leads to more severe pneumonia.<\/p>\n","protected":false},"excerpt":{"rendered":"
WASHINGTON The ongoing spread of bird flu in the United States has alarmed experts \u2014 not just because of human cases causing severe illness, but also due to troubling new instances of infections in cats. A sample of the virus found in a critically ill patient in the United States has shown signs of mutating […]<\/p>\n","protected":false},"author":2,"featured_media":452230,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6],"tags":[],"class_list":{"0":"post-452214","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-world"},"yoast_head":"\n