A California raw milk dairy that was previously linked to a fatal outbreak of bird flu in cats has now been linked to an E coli outbreak involving cheddar cheese, affecting nine people in three states.

The US Food and Drug Administration (FDA) said in an alert that more than half of the people sickened so far are children under age five. Three people have been hospitalized after contracting a dangerous strain of E coli – O157:H7 – with one developing hemolytic uremic syndrome, a condition that can lead to kidney failure.

The FDA said that bacterial samples in the people who became ill between September last year and February 2026 showed genetically similarities. Seven cases were reported in California, while both Florida and Texas each reported a case.

The farm identified in the outbreak is Raw Farm in Fresno, California, the largest producer of raw milk in the US. Earlier this month, the FDA identified the farm as the “likely source” of the E coli outbreak.

In December 2024, Raw Farm was identified as the source of H5N1 bird flu in three Los Angeles-area cats that had consumed raw milk. Two died, and fears were raised that that cats, like pigs, had cellular receptors which allow them to act as “mixing vessels for reassortment of avian and mammalian influenza viruses”.

The farm was also linked to the largest salmonella outbreak in more than a decade when, in 2024, at least 165 people were sickened.

In the cheddar cheese case, Raw Farm’s president, Aaron McAfee, told NBC News that he won’t voluntarily recall any of his products unless there’s “direct proof” linking to the illnesses.

No Raw Farm products have been reported to test positive for E coli and the FDA has not issued a mandatory recall of Raw Farm products, but it has recommended the producer remove cheese products from store shelves voluntarily.

“We’ve sampled 81 samples that we purchased off retail stores in California, where we continue to sell and those were all negative. If I had any concern, I would have issued a voluntary recall,” McAfee said.

An FDA spokesperson told NBC that the agency’s investigation is ongoing and it had issued “an outbreak advisory to inform consumers, restaurants and retailers of the current facts, and initiated an on-site inspection”.

Separately, the Centers for Disease Control and Prevention is advising people to “consider not eating this cheese while the investigation continues” and to wash any items and surfaces – like box shredders, knives and countertops – that may have touched the cheese.