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<\/div>Farm workers exposed to infected dairy cattle have been found to carry bird flu antibodies<\/p>\n
Helen King\/Getty Images<\/p>\n<\/div>\n<\/figcaption><\/figure>\n<\/p>\n
There may be more bird flu cases in humans in the US than we previously thought. Health departments in two states took blood tests of workers on dairy farms known to have hosted infected cattle and found that about 7 per cent of them have antibodies for the disease. This included people who never experienced any flu symptoms.<\/p>\n
Since March, a bird flu virus known as H5N1 has been circulating in dairy cows across the US. So far, 446 cows<\/a> in 15 US states have tested positive for the virus. Since April, 44 people<\/a> in the US have tested positive for H5 \u2013 the influenza subtype that includes H5N1. All but one of these cases<\/a> occurred in workers on H5N1-infected poultry or dairy farms.<\/p>\n To better understand how many farm workers may have contracted the virus, the US Centers for Disease Control and Prevention (CDC) collaborated with state health departments<\/a> in Colorado and Michigan to collect blood samples from 115 people working on dairy farms with H5N1-infected cattle. All of the samples were obtained between 15 and 19 days after cows on the farms had tested positive for the virus.<\/p>\n <\/p>\n Nirav Shah<\/a> at the CDC and his colleagues then removed seasonal influenza antibodies from the samples before testing them for the presence of H5N1 antibodies. They found H5N1 antibodies in eight of the samples, or about 7 per cent, suggesting that eight of the workers had been unknowingly infected with the virus. What\u2019s more, four of the workers didn\u2019t recall ever having symptoms.<\/p>\n \u201cThis is critical because, before this point, the recommendations for [H5N1] testing largely have focused on symptomatic workers,\u201d says Meghan Davis<\/a> at Johns Hopkins University in Maryland. \u201cWhen workers don\u2019t know that they are infected, they inadvertently may expose other people in their communities to the infection.\u201d<\/p>\n H5N1 is poorly adapted to infecting humans and isn\u2019t known to transmit between people. Still, more than 900 people globally<\/a> are reported to have had the virus since 2003, roughly half of whom died from it. Each of these infections offers the virus an opportunity to develop mutations that may make it more dangerous to people<\/a>.<\/p>\n \u201cWe in public health need to cast a wider net of who we offer a test,\u201d said Shah at a press conference today. \u201cGoing forward, the CDC is expanding its testing recommendation to include workers who were exposed [to H5N1] and do not have symptoms.\u201d<\/p>\n The agency is also recommending that antiviral medications be offered to asymptomatic workers who have a high-risk exposure, like those on dairy farms who may get raw milk splashed on their face. That way, if they do contract the virus, a lower amount of it will be circulating within them, which in turn lowers the risk of it spreading to other people. \u201cThe less room we give this virus to run, the fewer chances we give it to change,\u201d said Shah.<\/p>\n This data also highlights that many H5N1 cases are going undetected \u2013 a concern public health officials have long suspected to be true. Yet \u201cwe can\u2019t speculate on how many unidentified cases there may be\u201d until we have more data, said Shah.<\/p>\n The CDC is now analysing an additional 150 blood samples collected from veterinarians who work with cattle. When these results become available, they should provide us with a clearer picture of how many cases may be slipping through the cracks, said Shah.<\/p>\n Topics:<\/p>\n<\/section><\/div>\n