Health officials are investigating whether a Missouri man hospitalized with bird flu in early September may have infected several other people.
Testing is underway for five healthcare workers and one household member who came into contact with the infected person, all of whom showed mild respiratory symptoms. Outbreaks indicate significant spread of avian influenza viruses and the potential for human-to-human transmission.
On Friday, Missouri state and federal health officials stressed there is currently no evidence of human-to-human transmission. The Centers for Disease Control and Prevention said the immediate risk to the general public is still low.
Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, said there’s no need to worry unless or until one of those tests comes back positive.
“At this time, there is no evidence that this case in Missouri transmitted the virus to anyone,” epidemiologist Osterholm said. “I’m not saying it couldn’t have happened, but based on what we know so far, there is no ongoing transmission. There is no crisis.”
Osterholm said about 2% of Americans have respiratory symptoms during this time, which could be H5N1, COVID-19 or just the common cold. Blood and DNA test results, not symptoms, tell the whole story.
“Just because someone has symptoms of a respiratory illness doesn’t tell us anything about whether they’re more likely to have the flu,” he says. “At this point, we want to be careful not to be alarmist.”
So far this year, 14 people have been infected with H5N1 avian influenza in the United States. All but this person in Missouri were infected after close contact with known infected poultry or dairy cows.
Authorities do not know how the person became infected with H5N1. Their infections were first reported on September 6th.
Earlier this month, federal health officials said for the first time that the person hospitalized was an isolated case and did not appear to pose any additional risk.
Shortly afterward, Missouri officials identified a person in the same household who developed “similar symptoms” on the same day as the confirmed case, said Lisa Cox, communications director for the state Department of Health and Senior Services. . However, Cox said in an email that neither had typical “flu-like symptoms or conjunctivitis,” referring to bird flu symptoms that have been occurring across the United States this year.
He added that the timing of the onset of symptoms suggested a general infection, such as by wild birds, rather than human-to-human transmission. Another person reported limited contact with an infected patient, but that person did not report any symptoms before or after the visit.
The CDC announced Friday that state officials have identified 18 high-risk health care workers. Three of them reported mild respiratory symptoms.
One person tested negative for influenza A, which includes avian influenza. No laboratory tests were performed on the remaining two patients because they were beyond the 10-day follow-up period when test results could be related to previous exposure, Cox said. Their symptoms were also not severe enough to warrant medical examination.
Instead, the two health care workers provided blood samples to the CDC to be tested for H5N1 antibodies. H5N1 antibodies appear at least three weeks after symptoms subside.
Blood samples were taken from five health care workers, Cox said. The original person and their family contacts have already sent samples to the CDC. Samples from the five workers will be sent to a CDC laboratory in Atlanta for testing. But the remnants of Hurricane Helen moving through the southern United States are delaying the shipment of specimens, Cox said.
“This type of test is an additional diagnostic test to determine whether a person has an H5 infection,” she said. “However, among other limitations, we cannot determine the source or timing of any infection that may have occurred.”
Dr. Jesse Goodman, an infectious disease expert at Georgetown University, said seeing test results will be critical.
“We don’t yet know whether any of these other people are infected with H5 influenza or have actually been infected. It’s very important to find out.”
Goodman added that because it’s not clear exactly how H5N1 develops in people, public health workers should be more aggressive in testing people with mild or asymptomatic symptoms. “We need to actively promote it,” he said.
He also said testing for H5N1 should be more widespread, as he expects more people to be infected with the virus than are being detected. The Missouri case was discovered purely by chance because the person was tested for the flu, but that doesn’t happen all the time. When it came back as an unusual type, it was sent for further testing, which is also not typical, Goodman said.
“We cannot panic over this, but we need to see this as a warning shot and we need to lean forward in monitoring and preparedness,” he said. “Most public health threats are exaggerated by people. I feel like this one is being underestimated a little bit.”
Karen Weintraub contributed to this report.
(This story has been updated to add new information.)
