Five more people who presumably contracted the bird flu are being tested amid outbreaks in California's dairy industry, health officials confirmed Monday.
The five new possible positive cases are located in the state's Central Valley and are pending testing, according to the California Department of Health.
There are total of six confirmed cases in the state as of Monday, the department said in a news release. The individuals had direct exposure to infected dairy cattle at nine different farms and are experiencing mild symptoms like eye redness or discharge (conjunctivitis). No one has been hospitalized.
The health department said the specimens are expected to arrive for testing at the Centers for Disease Control and Prevention early this week.
"Given the amount of exposure to infected cows, evidence continues to suggest only animal-to-human spread of the virus in California," the health department wrote. "Based on CDC's genomic sequencing of three California bird flu cases, there is no evidence to suggest an increased ability for the virus to infect or spread between people."
Risk to general public is low
California officials said the risk to the general public remains low but warned that those who "interact with infected animals are at higher risk of getting bird flu."
There are no known links between the six confirmed cases, which suggests there is widespread transmission among dairy herds and that the infected cattle pose risks to people working near them.
One of the newly identified people who tested positive worked on the same farm as a previously infected person, but they worked in different areas of the facility and were not in close contact, the CDC said.
20 positive bird flu cases this year
Officials have identified 20 people across the U.S. infected with bird flu this year. Nearly all of them worked with infected dairy or poultry livestock. However, one person infected in Missouri has no known source of transmission, according to state and federal officials.
Blood test results are pending for close contacts of the person in Missouri, who had been hospitalized with the virus. The contacts include several health workers who treated the person for bird flu. Some of those workers came down with mild respiratory symptoms, but state and federal officials stressed there wasn't evidence of human-to-human transmission, which would mark a shift in virus transmission.
There are 100 dairy herds in central California that have reported confirmed cases of bird flu in cattle, the CDC said. The increase in infected cows on California farms has significantly altered the number of herds nationally with the virus. Nearly 300 herds across 14 states have confirmed bird flu cases.
Workers urged to wear N95 respirators, face shields
Health officials recommend livestock workers wear personal protective equipment, including N95 respirators, goggles, face shields and gloves.
The CDC is also ramping up its efforts to vaccinate livestock workers, who are at greater risk of contracting bird flu, against seasonal influenza.
Seasonal flu vaccines do not provide protection against bird flu. However, officials fear that a cross-reaction of both influenza viruses in the body can cause bird flu to mutate to spread more easily or cause serious illness.