An animal caretaker labels a blood sample that has been collected from a dairy calf vaccinated against bird flu at the National Animal Disease Center research facility in Ames, Iowa, July 31, 2024. /CFP
The U.S. Centers for Disease Control and Prevention (CDC) confirmed two human cases of H5 bird flu in California on Thursday, marking the first reported human cases in the state.
The cases occurred in individuals with occupational exposure to infected dairy cows. An investigation, led by California officials, is ongoing, according to the CDC.
At this time, there is no known link between the two confirmed cases, suggesting these are separate instances of animal-to-human transmission of the virus, the CDC reported.
CDC officials stated that new cases of bird flu in people exposed to infected animals are "not unexpected." They added that the risk to the public remains low.
The CDC continues to work closely with public health officials in California and other states to control the spread of H5N1 from infected animals to humans.
H5N1 bird flu was detected in cows in the United States for the first time this year. The virus is widespread in wild birds and has caused ongoing outbreaks among poultry in the country since 2022. It has occasionally caused infections in people who work with infected animals, such as dairy and poultry workers.
Dairy cows stand in a field outside of a milking barn at the U.S. Department of Agriculture's National Animal Disease Center research facility in Ames, Iowa, August 6, 2024. /CFP
So far, 16 human cases of H5 have been reported in the United States in 2024. Six of the reported human cases were linked to exposure to sick or infected dairy cows. Nine cases had exposure to infected poultry, according to CDC.
Across the U.S., more than 250 dairy herds have been infected in 14 states since the outbreak of H5N1 avian influenza was confirmed in March. Avian influenza has been spreading in wild and domestic birds in the U.S. for several years but recently was found in dairy cows.
Before this year, only one human case of bird flu had been detected in the U.S., involving a Colorado poultry worker who fell ill in 2022. Additionally, a person in Missouri was infected, though that individual had no known contact with animals, and the source of the illness remains undetermined.
(With input from agencies)