At least one person in Texas has been diagnosed with bird flu following contact with dairy cows presumed to be infected, state officials said on Monday.

The announcement adds a worrying dimension to an outbreak that has affected millions of birds and sea mammals worldwide and, most recently, cows in the United States.

So far, there are no signs that the virus has evolved in ways that would help it spread more easily among people, federal officials have said.

The patient’s primary symptom was conjunctivitis; the individual is being treated with an antiviral drug and is recovering, according to the Centers for Disease Control and Prevention.

The Department of Agriculture announced the first cases in dairy herds in Texas and Kansas last week, and then, a few days later, in an additional herd in Michigan. Preliminary testing suggests that cows in New Mexico and Idaho may also be infected.

The virus has been identified as the same version of H5N1, an influenza subtype, that is circulating in North American birds.