Avian influenza A (H5N1) was identified in someone exposed to dairy cattle presumed to be infected with avian influenza, according to DSHS.
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There have been no reports of person-to-person transmission.
Texas Department of Health and Human Services epidemiologist Dr. Varun Shetty said they don't know how the cow got the dairy worker sick.
"That's still a question we don't have the answer to right now," Shetty said. "It's something that we're hoping to find out."
He said the CDC looked at the same to see if the virus had mutated.
"The good news is that it has not," Shetty explained. "It's the same strain that's been circulating among wild birds and backyard flocks that we've seen for some time now, and it hasn't had any new changes."
Despite the transmission, the agency said the risk remains low, and the virus doesn't spread from human to human. UTHealth Houston epidemiologist Catherine Troisi said if the virus did mutate, it could cause a concern.
"Influenzas are a particularly tricky virus," Troisi explained. "It mutates easier than even COVID does. We're keeping an eye on it, and hopefully, nothing will happen."
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The CDC tested the patient last week after the person reported having eye inflammation, their only symptom, which is being treated by the antiviral drug oseltamivir.
This is the second human case of H5N1 ever reported in the U.S., and the first was linked to cattle.
In March, U.S. officials said milk from dairy cows in the Texas Panhandle and Kansas tested positive for bird flu.
Officials with the Texas Animal Health Commission confirmed the flu virus is the Type A H5N1 strain, known for decades to cause bird outbreaks and infect people occasionally. The virus affects older dairy cows in those states and New Mexico, causing decreased lactation and low appetite.
According to the U.S. Department of Agriculture, the commercial milk supply is safe.
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Dairies are required only to allow milk from healthy animals to enter the food supply, and milk from sick animals is being diverted or destroyed. Pasteurization also kills viruses and other bacteria, and the process is required for milk sold through interstate commerce, the agency said.
"At this stage, there is no concern about the safety of the commercial milk supply or that this circumstance poses a risk to consumer health," the USDA said in a statement in March.
At the state level, DSHS said it provides guidance to affected dairies about how to minimize workers' exposure and how people working with sick cattle can monitor for flu-like symptoms and get tested.
People with these infections can have symptoms ranging from mild, such as eye infection and upper respiratory issues, to severe, such as pneumonia and death.
The Associated Press contributed to this report.