Federal health officials in Atlanta are testing blood from Missourians who came in contact with a person with bird flu to see if the virus can spread among humans, instead of spreading from animals associated with the outbreak.
The U.S. has seen 14 reported cases of the H5N1 avian flu virus, which has been reemerging in humans this year. The virus has spread among poultry and cattle livestock, and before the Missouri patient, every reported case in humans had been in those who had direct contact with animals.
A routine flu screening in late summer found the virus in the person, who had been hospitalized for another illness. Unlike the other reported cases, this person did not report being in recent contact with animals.
“That's of course cause for interest,” Department of Health and Senior Services spokeswoman Lisa Cox said. “I think the main reason for interest in this … is the fact that there is no known source at this point, and there is a lot of curiosity about human-to-human transmission since that has not occurred yet.”
Health workers at the department discovered the person was infected after the patient had gone home from the hospital. The hospital, local public health agency and state health officials worked to find people who had been in contact with the patient and had since developed flu-like symptoms.
Through contact tracing, or tracking down people who had been in contact with the patient, officials found five health care workers who had unexplained symptoms that could have arisen from contact with the patient. Health workers have sent blood samples from those five, along with the original patient and another person who had close contact with them, to the Centers for Disease Control and Prevention’s headquarters in Atlanta to test for antibodies, which could prove they had the virus.
“Everyone wants to study this as much as possible and find a source,” Cox said. “But at the same time, it's not uncommon to to actually conclude an investigation and not actually determine a source.”
The health workers could have developed COVID-19 or other respiratory infections instead, she said. The coronavirus had been spreading throughout the summer.
H5N1 outbreaks have been reported in poultry flocks this year, but not in cattle. The virus has also been found in wild birds in other years.
Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, said it’s likely the workers had more common respiratory illnesses.
“I think at this point it's really important just to take a step back, because I've seen a lot of comments in the media about the fact that this is an outbreak or a cluster of bird flu cases,” he said. “In fact, there's no evidence of that whatsoever.”
It’s not unheard of for people to develop flu variants without known contacts with infected animals, he said.
“If I were betting, I'd probably say that none of them were infected, but if they were, then we need to know that,” Osterholm said. “The real concern would be are we starting to see person-to-person transmission of H5N1? And at this point, we just don't have any evidence of that.”
Health workers don’t know when the CDC will have results of the tests, Cox said, although state officials are staying in contact with the federal agency. Hurricane Helene, which battered the southeast in late September, delayed the shipment of the blood.
