Earlier this month, a dairy worker in Texas tested positive for bird flu, aka avian influenza, amid an outbreak of the virus among dairy cattle. It's the first time this virulent strain of bird flu — referred to as highly pathogenic H5N1 — has been detected in cows and the first documented cow-to-human transmission of an avian influenza virus, according to the U.S. Centers for Disease Control and Prevention. It's also only the second case of bird flu in a human in the United States.
Once the bird flu gets into a human, “it is almost never spread to anyone else,” says Schaffner. However, “there are ultra-rare instances of transmission from a person very sick with bird flu to a family member or caregiver.” When does happen, it does not lead to continued spread between people 'because the virus doesn’t have the capacity to spread easily from person to person,” says Schaffner.