California reports two confirmed cases of bird flu infection in Central Valley dairy workers

California health officials reported two confirmed cases of H5N1 bird flu infection in Central Valley dairy workers on Thursday afternoon.

Both cases were in Tulare County — the largest dairy producing county in the nation. With more than 600,000 dairy cows, the county generates roughly 30% of the state’s milk production.

Officials say a presumptive case they had announced Thursday morning has been confirmed as H5 by the U.S. Centers for Disease Control and Prevention, as well as an additional case.

These are the first two cases of bird flu identified in California. On Saturday, the California Department of Public Health reported that a third possible human case of bird flu had been identified in a Central Valley individual who had contact with infected dairy cattle. Specimens are being sent to the CDC to undergo testing.

Erica Pan, an epidemiologist with the California Department of Public Health, said there was no known link or contact between the two cases, and the two people infected did not work at the same dairy farm. She said there was no evidence of human-to-human spread.

She said both workers had mild symptoms, and the risk to the general public remains low, although a news release sent out by the department noted that people who interact with infected animals are at higher risk of getting bird flu.

These two cases bring the total number of humans infected with bird flu by diseased dairy cattle to six. Since the beginning of the year, there have been 16 cases of bird flu reported in the U.S. Nine were associated with exposure to poultry infected with avian influenza A, or H5N1.

In one case in Missouri, investigators have been unable to determine the source of viral infection — the person had no known contact with dairy, poultry or raw milk.

“Ongoing health checks of individuals who interact with potentially infected animals helped us quickly detect and respond to this possible human case. Fortunately, as we’ve seen in other states with human infections, the individual has experienced mild symptoms,” Dr. Tomás J. Aragón, director of the public health department and state public health officer, said in a news release.

As of Friday , officials had reported 56 infected dairy herds in the state since the virus was first reported in a Central Valley herd in late August. Across the nation, there have been 256 herds officially reported to have the virus, across 14 states, according to the U.S. Department of Agriculture.

Experts say they are not surprised that workers have been infected.

“With the rapid spread and increased detection of more infected herds in California, it’s to be expected,” said Rick Bright, a virologist and the former head of the U.S. Biomedical Advanced Research and Development Authority. “This outbreak of H5N1 is getting more concerning by the day.”

John Korslund, a retired USDA veterinarian epidemiologist, agreed.

“This is expected,” he said in an email. “If testing could be done on every newly infected farm as soon as the first employees showed any clinical signs (eyes or respiratory), we’re pretty confident California could have 5-10 human cases a DAY, given the number of people newly exposed daily. The level of human testing is abysmally low, and in general testing is done too late when it is done at all.”

He said the bigger question to be asked is the “degree of onward spread to family members, and other non-exposed families.”

He noted the case in Missouri, where reports have suggested that an individual living in the infected person’s house had similar symptoms but was not tested. In addition, several healthcare workers who’d had contact with the infected person also came down with similar symptoms.

They were not tested, either.

“Hopefully all the Missouri case publicity will increase pressure on local public health departments to conscientiously make complete and follow-up visits to affected families,” he said in an email. “Sporadic human spill-over (from cows) is not a huge deal, but as evidence builds for human-to-human spread, the necessity for aggressive investigations mounts. “

Pan, the state epidemiologist, said state and local health investigators had been and were currently “contact” tracing — looking for others who may be vulnerable.

“I think it’s probably general knowledge that a lot of workers live together,” she said. “So, you’re really interviewing people about who they spend time with, who they live with. Obviously, for most or many infectious diseases, the highest-risk people are people that you live with, or you’re intimate with, or other people you spend close time with.”

She said the two California dairy workers’ only symptom was conjunctivitis, or pink eye.

Neither worker reported respiratory symptoms, nor were they hospitalized. Both people have been told to isolate at home and have been offered antiviral medication, Pan said. She said she knew one of the two started taking the medications; she did not have information about the other person.

“It’s early on in the situation,” she said. Health officials, and even the patients, only recently found out about the infections.

Pan did not provide any more information about the workers — such as age, gender or location — to protect their privacy.

Asked whether workers were wearing personal protective equipment despite the record-breaking heat throughout the state, she said reports suggested they were. But even if they are wearing safety glasses over their eyes to protect themselves from milk splash, droplets can get in.

She said drops of infected milk directly to the eye were the most likely route of exposure for these workers.

Officials say that people who have been exposed to infected animals should look out for eye redness (conjunctivitis), cough, sore throat, runny or stuffy nose, diarrhea, vomiting, muscle or body aches, headaches, fatigue, trouble breathing and fever in the 10 days after exposure.

If they start to feel sick, they should isolate themselves and contact their local public health department.

“This virus is out of control,” said Bright, adding that he hopes California will be “more forthcoming and transparent with data” than what he’s observed elsewhere.

“It is time for urgent and serious leadership and action to halt further transmission and mutation. The concept of letting it burn out through food animals, with unmonitored voluntary testing, has failed,” he said. “There are pandemic playbooks that we need to dust off and begin to implement.”