The new study is more evidence that the official U.S. tally of confirmed human bird flu infections — 68 in the last year — is likely a significant undercount, said Dr. Gregory Gray, an infectious disease researcher at the University of Texas Medical Branch in Galveston.
In those studies, several of the infected workers remembered having symptoms of H5N1 bird flu, while none of the veterinarians in the new paper recalled any such symptoms.
He said it shows that officials cannot fully understand bird flu transmission by only tracking people who to go to medical clinics with symptoms.
“This means that people are being infected, likely due to their occupational exposures, and not developing signs of illness and therefore not seeking medical care,” Gray said.
However, if the virus changes or mutates to start making people very sick, or to start spreading easily from person to person, that would be “a completely different story,” Nolting said.
