Health officials are trying to find out how a person in Missouri was sickened by H5 avian influenza, or bird flu. It’s the latest twist in concerning new behavior of the virus, which was detected in farm workers, cows, and milk earlier this year.

First U.S. Human Bird Flu Case Reported With No Animal Contact, but all had mild symptoms, such as conjunctivitis (pink eye), or signs of the flu, like a sore throat and runny nose. Also, all of the infected people had contact with poultry or cattle. Those cases were in farmworkers in Colorado, Michigan, and Texas.

Missouri health officials reported that the person had another medical condition and was hospitalized on Aug. 22, treated with antiviral flu medicine, and has now recovered. Follow-up testing by the CDC confirmed the diagnosis, and the agency is doing more tests to learn more about the specific strain.

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Missouri health officials are still investigating how the person may have been exposed to bird flu. There have been no detections of bird flu in cattle in Missouri, but it has been found this year in commercial and backyard poultry flocks. Close contacts of the Missouri patient have shown no signs of the virus. It’s possible that the infection stems from close contact with an infected migratory bird, Michael Osterholm, PhD, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, told USA Today.

This is the first case of bird flu detected by the nation’s influenza surveillance system, in which flu samples from a variety of health centers, like health departments and emergency rooms, are extensively tested for detailed information about viral strains. The other human cases of bird flu were identified this year through a testing program for people linked to animal outbreaks.

So far, there has been no evidence of human-to-human spread of bird flu, and health officials continue to say the risk of bird flu to humans is low. The FDA said that the commercial milk supply is safe because testing of pasteurized dairy products has found only nonviable signs of the virus.