As H5N1 bird flu spreads among dairy herds and birds migrating south from California, health officials announced Friday six more human cases: five in California and one in Oregon — the first in the state.

A seventh presumptive case from California pending confirmation from the US Centers for Disease Control and Prevention.

All reported cases have been described as mild and each person is believed to have contracted the disease from infected animals or birds. In California, infections have occurred among dairy workers. In Oregon, the patient was a poultry worker.

Read more:Canadian teenager infected with H5N1 bird flu in critical condition

California State Epidemiologist Erica Pan said that while the announcement of five cases today may sound like a sudden burst or acceleration in cases, it was an artifact of state reporting deadlines. Three cases were confirmed by the CDC on Wednesday, after California’s reporting deadline. The other two were confirmed on Thursday – a day when California does not report on the number of cases.

And there was also a holiday on Monday, which slowed down reporting even more.

“I would still call these sporadic animal or human infections, and there is still no evidence of human-to-human transmission,” she said. “These are all workers who are at risk of exposure based on their exposure at work.”

In the case of Oregonthe person contracted the disease from a previously reported outbreak of infected commercial poultry operations in Clackamas County. A statement from the Oregon Health Authority said “there is no evidence of person-to-person transmission and the risk to the public is low.”

The agency said the person is fully recovered and has been treated with oseltamivir, an antiviral drug. The health agency also prescribed the antiviral drug to people who lived in the same house as the patient.

Since March, the US Centers for Disease Control and Prevention has said 52 people have been infected with the H5N1 virus. Dairy cattle were the source for 30 of those cases, poultry for 21. The source of one more case in Missouri remains unknown.

Read more:Bird flu virus found in Los Angeles County sewage

In addition, a teenager from British Columbia was infected by an unknown source and has been hospitalized in critical condition since Friday.

Twenty-six cases have been identified in California, including the most recent five. All had been in contact with infected dairy cows.

WastewaterScan – an infectious disease monitoring network led by researchers at Stanford University and Emory University, with laboratory support from Alphabet Inc.’s Verily. for life sciences – tracks 28 treatment sites in California. All but seven have detectable amounts of H5. It’s not clear what the source is in each system, but experts say it could be from unpasteurized milk, wild bird droppings or contaminated discarded animal products.

Cities and municipalities that have detected the virus since early November are: Gilroy, Indio, Lompoc, Los Angeles County, Los Angeles, Marina, Merced, Napa, San Francisco, Ontario, Palo Alto, Redwood City, Riverside, Sacramento, San Diego, San José, Santa Cruz, Southeast San Francisco, Sunnyvale, Turlock and Vallejo.

This story originally appeared in Los Angeles Times.