The Centers for Disease Control and Prevention (CDC) announced Thursday that there is no evidence of human-to-human transmission of the H5N1 bird flu virus in a recent Missouri case, despite a rise in infections among farmworkers. The announcement comes after a monthslong investigation into the hospitalization of a Missouri patient, who tested positive for bird flu in August. The CDC's findings offer reassurance, although concerns about the virus spreading among animals and humans remain.
The Missouri patient, whose identity has not been released, had no known contact with dairy cows or poultry, according to CDC officials. Bird flu has primarily affected farm animals, wild birds, and farmworkers. The virus has infected 31 people in the U.S., most of whom had direct exposure to animals. Several health workers who treated the Missouri patient reported respiratory symptoms, raising concerns about potential transmission. However, all five symptomatic workers tested negative for the virus, according to Dr. Demetre Daskalakis, head of the CDC's National Center for Immunization and Respiratory Diseases.
"From the perspective of where we are with this investigation, I think we've got the conclusion," Daskalakis stated during a media briefing.
While the Missouri case did not lead to further transmission, health officials remain vigilant. One blood test from a household contact of the infected patient suggested the presence of H5 antibodies, but a second test was inconclusive. Dr. Nirav Shah, the CDC's principal deputy director, indicated that this was not definitive proof of transmission between individuals. "We arrived at the same conclusion using different lines of evidence," Shah said, confirming that both individuals likely contracted the virus from the same source, possibly an infected animal or animal product.
As bird flu continues to spread in the U.S., particularly among dairy herds and poultry, the risk to the general public remains low, according to the CDC. However, those who work directly with animals are at higher risk. The CDC confirmed that the outbreak has infected 333 dairy herds across 14 states, with California being the hardest hit, accounting for 137 infected herds.
Recent reports also identified two poultry workers in Washington state who became ill after culling chickens at an infected farm. Authorities expect more cases to emerge as the virus spreads. Washington state officials have invited CDC teams to assist in their investigation, while California has also requested federal help due to the large number of infections in the state.
Dr. Erica Pan, deputy director for the California Department of Public Health's Center for Infectious Diseases, highlighted the state's proactive approach to monitoring workers. "These are proactive health checks," Pan said. "It's about actually checking with them, 'How are you doing? Are you having symptoms?'"
Though the infected individuals in the U.S. have shown only mild symptoms, including conjunctivitis and upper respiratory issues, public health experts are watching the outbreak closely. Antiviral treatments such as Tamiflu have been offered to those infected. Shah stressed that while the current risk assessment for the general public remains low, the CDC is continuing to monitor the situation as more cases are identified.
In total, human bird flu cases have been confirmed in several states, including Texas, California, Colorado, Michigan, Missouri, and Washington. However, the CDC emphasized that there is no evidence of human-to-human transmission in these cases, and that the virus spread has primarily occurred among people exposed to infected poultry or dairy cattle.
