Blood tests confirm a second person in Missouri caught bird flu without exposure to infected animals, but questions remain

Blood tests of several people who were in contact with a patient in Missouri who caught H5N1 bird flu without any known exposure to infected animals reveal at least one of them — a person who lived in the same house and had symptoms at the same time — also had the virus, according to two sources with knowledge of the investigation.

Blood tests of several people who were in contact with a patient in Missouri who caught H5N1 bird flu without any known exposure to infected animals reveal at least one of them — a person who lived in the same house and had symptoms at the same time — also had the virus, according to two sources with knowledge of the investigation. H5N1 is a type of influenza that’s rare in humans, but is highly contagious and deadly in several species of animals, including poultry and dairy cattle, raising fears that it could mutate and become a virus that preys on people, too. The specialized blood tests, which were conducted by scientists at the US Centers for Disease Control and Prevention in Atlanta, looked for immune proteins called antibodies made in response to an infection. These antibodies confirm that a person has had a past infection with a particular pathogen. The results were shared more widely with public health officials, scientists and the media in several calls hosted by health officials on Thursday morning. The tests were conducted to understand whether the Missouri patient – who is the first person to catch H5N1 influenza in the United States without any apparent exposure to infected animals – infected anyone else. So far, the H5N1 virus has not been able to spread easily between people. Infectious disease experts fear that if the virus gains that ability, it could touch off a new pandemic. While the results don’t definitively rule out human-to-human transmission of the virus, they do suggest it isn’t common or widespread and that it didn’t happen in a health-care setting where caregivers have close physical contact with patients. CDC officials said. Even though a person living in the patient’s household was also positive, the CDC says the timing of their illness suggests that both had a common exposure rather than one catching it from the other. Around the United States, more than two dozen people have tested positive for H5N1 flu so far this year and nearly all of them have reported exposure to infected dairy cows or chickens, according to the CDC.