Health workers in Missouri tested after person hospitalized for bird flu

Health officials are investigating whether a person in Missouri who was hospitalized with bird flu in early September might have infected a handful of others.

Testing is ongoing among five health care workers and a household member exposed to the infected person who all came down with mild respiratory symptoms. A cluster of infections would mark a significant expansion of the avian influenza virus , indicating that it could transmit from person to person.

On Friday, Missouri and federal health officials stressed there is no current evidence of human-to-human transmission. The immediate risk to the general public is still low, the Centers for Disease Control and Prevention said.

Michael Osterholm, who directs the Center for Infectious Disease Research and Policy at the University of Minnesota, said he sees no cause for concern unless or until any of those tests comes back positive.

"At this point we don’t have any evidence that this one case in Missouri has transmitted the virus to anyone," said Osterholm, an epidemiologist. "I’m not saying it couldn’t have happened, but based on what we know so far, we’ve not had ongoing transmission. There’s no crisis."

This time of year, Osterholm said, roughly 2% of Americans have respiratory symptoms, which could be H5N1 or COVID-19 or simply a cold. The blood and DNA test results will tell the story, not symptoms.

"Just because somebody has symptoms of respiratory illness doesn’t tell me anything about 'is it likely or not likely to be flu,'" he said. "At this point, we want to be careful not to become alarmist."

So far this year, 14 people across the U.S. have been infected with H5N1 avian influenza. All but the Missouri person was infected after coming into close contact with poultry or dairy cows known to be infected.

Officials don't know how that person became infected with H5N1. Their infection was first reported Sept. 6 .

Earlier this month, federal health officials had first said the person hospitalized was likely an isolated case that didn’t appear to pose additional risk.

Soon after, Missouri officials identified that a person in the same household developed “similar symptoms” on the same day as the confirmed case, according to Lisa Cox, communications director for the state Department of Health and Senior Services. But neither person had typical “flu-like symptoms or conjunctivitis,” Cox said in an email, referring to symptoms seen in the prior bird flu cases across the U.S. this year.

The timing of the onset suggested common exposure, such as from a wild bird, rather than person-to-person transmission, she added. Another person reported limited contact with the infected patient, but that person reported no symptoms either before or after the visit.

On Friday, CDC said state officials identified 18 health care workers who had higher risk exposure. Three of those workers reported reported mild respiratory symptoms.

One person tested negative for influenza A, which includes bird flu. The other two weren’t clinically tested because they passed the 10-day follow-up period when those test results could be connected with a previous exposure, Cox said. Their symptoms also weren’t severe enough for them to seek medical testing.

Instead, those two health workers have provided blood samples for CDC to test for H5N1 antibodies, which show up at least three weeks after symptoms have passed.

Blood samples have been collected from five health care workers, Cox said. The original person and their household contact have already had their samples sent to the CDC. The five workers’ samples are set to be sent to CDC’s laboratory in Atlanta for testing. However, the remnants of Hurricane Helene passing through the American South are delaying shipment of the specimens, Cox said.

“This type of testing is an additional diagnostic test that H5 infection has occurred in the person,” she said. “However, among other limitations, it will not be able to determine either the source or timing of any infection that may have occurred.”

Seeing the results of the tests will be crucial, said Dr. Jesse Goodman, an infection diseases specialist at Georgetown University.

"We don’t know yet if any of these other people do have H5 influenza or did get it − that’s really important to investigate," he said.

Goodman added public health workers should be more aggressive about testing people with mild or no symptoms, because it's not clear exactly how H5N1 manifests in people. "It needs to be pursued aggressively," he said.

He also said there should be more widespread testing for H5N1, because he expects more people likely have it than have been discovered. The case in Missouri was caught purely by chance, because the person's flu was tested, which doesn't always happen. When it came back as an unusual type, it was sent for further testing, which also is atypical, Goodman said.

"We can’t view this with panic, but we need to view this as a warning shot and we need to lean forward with our surveillance and our preparedness," he said. "Most public health threats, people overblow them. This one I feel like has been a little underplayed."

Karen Weintraub contributed to this report.

(This story was updated to add new information.)

This article originally appeared on USA TODAY: Health workers in Missouri tested after person hospitalized for bird flu