CHICAGO—California reported a third human case of bird flu on Wednesday in a dairy worker who had contact with infected cattle and said the state identified two more possible cases in people.

Officials in the most populous U.S. state expect to confirm additional cases in people who have contact with infected dairy cattle, the California Department of Public Health said.

The outlook for more cases follows a surge in infections of dairy cows in the biggest milk-producing U.S. state.

Nearly 300 dairy herds across 14 states tested positive so far this year, with about a third of the cases found in California since late August, according to the U.S. Department of Agriculture. Pasteurized milk and dairy products remain safe to consume, California’s public health department said.

A total of 16 people exposed to dairy cows and poultry have tested positive nationwide in 2024. Another person in Missouri who had no immediate known contact with animals also tested positive.

The U.S. Centers for Disease Control and Prevention said that cases in people exposed to infected animals are “not unexpected.” Risks to the general public are low, the CDC said.

The virus’ jump to cattle and infections of farm workers have worried scientists and federal officials about the risks to humans.

There is no known link or contact between any of California’s confirmed or possible cases, suggesting the virus spread from animals to humans in the state and not from person to person, the California Department of Public Health said.

All of the people had contact with animals at different farms and experienced mild symptoms, including eye redness or discharge, the department said. It said none were hospitalized.

Last week, California reported two human cases in dairy workers.

In those cases, there were no genetic changes to the virus observed that are known to be associated with an increased ability to infect or spread between people, the CDC said. There were also no changes known to reduce susceptibility to antiviral medications, the agency said.

By Tom Polansek