California health officials on Tuesday reported a possible case of bird flu in a child with mild symptoms.

The child lives in Alameda County, part of the San Francisco Bay Area, and tested positive for the virus despite having no known contact with an infected animal.

Officials with the California Department of Public Health said in a news release that they are investigating whether the child could have been exposed to wild birds. It’s considered a “possible” case until the positive test is confirmed by the Centers for Disease Control and Prevention.

Fifty-three people have been confirmed with bird flu in the U.S. this year, according to the CDC; all but one had been exposed to infected poultry or dairy cows.

The child experienced mild upper respiratory symptoms and is recovering at home after receiving treatment, the health department said. No person-to-person spread of the virus has been detected, and the child’s family members all tested negative. A bird flu test on the child four days after the positive result came back negative.

Bird flu has been spreading rampantly in poultry since 2022 in the worst such outbreak the U.S. has ever experienced. More than 108 million birds have been sickened, killed or culled. Cases in dairy cows began to crop up in March and have since been reported in 15 states. The virus was found in a pig for the first time last month.

Cases in people — nearly all among farmworkers — have been confirmed in seven states, with Oregon reporting its first human case last week. Such infections remain rare, however, and health officials maintain that the risk to the public is very low.

In the case of the California child, tests for other respiratory viruses also came back positive at the same time, so health officials said those viruses could have caused the child’s symptoms.

The child’s family members were confirmed to have the same common respiratory viruses, and they are being treated with preventive medication, according to the officials’ news release.

Health officials notified other people who had contact with the child and offered preventive treatment and testing. The child attended day care with mild symptoms, the officials said.

Tomás Aragón, director of the state’s health department, said in a statement that he understands that people might be concerned, but he reassured the public that, “based on the information and data we have, we don’t think the child was infectious — and no human-to-human spread of bird flu has been documented in any country for more than 15 years.”

California represents the largest share of human bird flu cases in the U.S. so far, with 27 confirmed, not counting the child in Alameda County. Washington has recorded 11 cases, and Colorado 10. Levels of testing and surveillance differ by state, however, which could explain some of the discrepancy.

In Canada, health officials reported the country’s first human case of bird flu last week, in a teenager hospitalized and in critical condition. The teen didn’t have any exposure to farm animals but was around dogs, cats and reptiles, officials said.