This article has been revised to include details about a second infection.

Health authorities from both the state and federal levels have reported that two dairy farm workers in California have tested positive for bird flu.

These infections represent the first human cases in California this year, amidst a nationwide surge that has now impacted 16 individuals in total. There is no connection between the two workers, as they were employed at different dairy farms with infected livestock. According to a statement from the Centers for Disease Control and Prevention (CDC), it appears that the H5N1 strain of avian influenza, which has been spreading among cows in California, was transmitted from the cattle to the workers.

Both individuals had interactions with infected cows in the Central Valley, which is known as California’s primary region for dairy production. The state is the largest producer of milk in the United States.

The infected workers exhibited mild symptoms, such as redness of the eyes, as reported by the California Department of Public Health (CDPH). This eye symptom has been observed in other livestock workers who contracted bird flu in the country. However, CDPH indicated that neither worker showed any respiratory problems and neither required hospitalization.

Earlier on Thursday, health officials had already identified one worker suspected of having bird flu after they tested positive at a local facility. Follow-up tests conducted by the CDC confirmed this worker had H5N1, while the second worker also tested positive. State officials had been investigating the second case and sent samples to the CDC, confirming this additional positive result.

Both federal and state health officials have emphasized that the overall risk to the general public remains low.

Before the cases in California, 14 individuals across various states had contracted bird flu since the spring, primarily among farmworkers who had close contact with infected animals.

Since late August, California has seen dairy herds afflicted with bird flu, with state officials reporting 44 infected dairies as of Tuesday.