The USA reports second human case of highly pathogenic H5N1 avian influenza (Hpai A/H5N1) associated with the epidemic that affected dairy cows in several states of the country. The infection was confirmed by the Centers for Disease Control and Prevention (CDC) in a dairy worker in Michigan. The man, the CDC reports, “reported only ocular symptoms“, as happened to the Texas worker suffering from hemorrhagic conjunctivitis, believed to be the first human case of Hpai A/H5N1 linked to the epidemic among cows in the United States, as well as the first person in the world to have contracted the avian virus from a bovine.
“Based on the information available – underline the CDC – this infection does not change the current assessment of the risk that H5N1 avian influenza poses to human health“. The agency continues to consider it “low for the general population,” while people with close or prolonged, unprotected exposures to infected birds or other animals (including livestock), or to environments contaminated by infected birds or other animals, run a greater risk of infection”. For these categories, the CDC highlights “the importance of recommended precautions”.
The Michigan worker, who had been monitored because the virus was circulating among the cattle of the company where he is employed – the CDC reconstructs – reported symptoms to the local health authorities. Two samples of biological material were taken from the patient, one from the nose and the other from the eyes. The nasal one tested negative for the influenza virus in tests carried out at the state health department laboratory. The ocular sample was sent to the CDC, whose laboratories are among the few centers that can subject the samples to the CDC A(H5) test. The test confirmed the avian virus infection, while the nasal sample was again negative for influenza also on CDC reanalysis.
“They are underway attempts to sequence the virus in the ocular sample“, add the CDC. “In case of a positive outcome, the results will be made available within 1-2 days. Further genetic analysis will try.” understand whether the pathogen shows “any mutations that could change the agency’s risk assessment”.
The CDC explains that “conjunctivitis has also been associated with previous human infections with avian influenza A viruses” and therefore falls among the symptoms evaluated by the agency for the diagnosis of H5N1 infection as part of ongoing surveillance. “Although it is not known exactly how eye infections result from exposure to the avian virus”, for the CDC “they could be due to contamination of the eyes” perhaps reached by “a splash of contaminated fluid”, or caused by “contact between the eyes and something contaminated with the virus, such as a hand. Indeed, high levels of the A/H5N1 virus have been found in unpasteurized milk from infected cows.
“Possible other human cases, but overall risk remains low”
“Given the high levels of H5N1 virus in raw milk from infected cows and the extent of its spread in dairy cows” in the United States, “additional human cases” of avian influenza may be identified, “similar” to those in the US two workers in the dairy sector have been affected so far, the CDC points out.
“Sporadic human infections without ongoing spread – specify the CDC – will not change the risk assessment for the general population”, which the agency continues to consider “low”.
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