More than half of the domestic cats on a Texas dairy farm that were fed unpasteurized milk from cows infected with the bird flu got sick and died, according to a preliminary report released Monday by the Centers for Disease Control and Prevention (CDC).

The report focused on early findings in the CDC investigation into the spread of bird flu through the cattle industry this year. Scientists reported that in mid-March, about 24 cats were fed raw milk at a Texas farm before the cows were known to be sick. One day after the cows showed visible signs of illness, the cats also became sick, and one to two days later, more than half of the cats grew ill and died.

In postmortem examinations of two of the dead cats, scientists observed signs of a “depressed mental state, stiff body movements, ataxia, blindness, circling, and copious oculonasal discharge.” Neurologic exams of affected cats also showed the “absence of menace reflexes and pupillary light responses with a weak blink response,” the scientists wrote.

The scientists said the new findings raise concerns about the possible cross-species and mammal-to-mammal transmission of the highly pathogenic avian influenza A (H5N1). The new report differs from previous studies that have suggested cows were not very susceptible to infection. On the contrary, the cattle show signs of apparent systemic illness, reduced milk production, and “abundant virus shedding in milk.”

“The magnitude of this finding is further emphasized by the high death rate (≈50%) of cats on farm premises that were fed raw colostrum and milk from affected cows,” the scientists wrote.

The highly pathogenic avian influenza (HPAI) first entered the country in late 2021, and infections in cattle have recently rocked the industry. Infections have been observed in cattle on farms in Texas, Kansas, Michigan, Idaho and Ohio, where the infected cows were transported, suggesting a cow-to-cow transmission.

The first human case associated with the infections in the cattle and bird populations was reported last month. A worker on a commercial dairy farm in Texas developed conjunctivitis, commonly known as pink eye, on March 27 and then tested positive for HPAI, the CDC said. The patient did not report any other symptoms and was not hospitalized. The person received antiviral treatment and is recovering, and the patient’s household members have not become sick, the CDC said.

“No additional cases of human infection with the HPAI A(H5N1) virus associated with the current infections in dairy cattle and birds in the United States, and no human-to-human transmission of HPAI A(H5N1) virus have been identified,” the CDC said.

The CDC said the risk remains low, but recommended people with jobs or recreational activities that could expose them to infected birds, cattle or other animals are at higher risk and should take precautions.

The virus historically has shown to be deadly, killing more than 50 percent of its human victims from 2003 to 2016. The current outbreak has spread to affect 82 million birds in 48 states, the worst outbreak of bird flu in U.S. history.