Bird flu pops up in Texas

According to Lara Anton, a spokesperson for the Texas Department of State Health Services, the patient infected with bird flu worked directly with sick dairy cows. "We have tested around a dozen symptomatic people who work at dairies, and only the one person has tested positive," she said.

The virus was identified as H5N1, a subtype of influenza that is circulating in North American birds, marking the second case of H5N1 found in a person in the United States. As of Monday, the virus has been confirmed in 11 herds of cattle across four states: Texas, Kansas, Michigan, and New Mexico, CDC said. Cows in Idaho may also be infected.

Sid Miller, commissioner of the Texas Department of Agriculture, said it's unclear whether the patient was infected specifically by a dairy cow or through the same source that infected the dairy cows, which seems to be dead waterfowl on the property.

The patient's primary symptom was conjunctivitis. According to Nirav Shah, principal deputy director of CDC, the patient has been treated with the antiviral oseltamivir, sold as Tamiflu, and is doing well. Shah added that the patient was told to isolate in order to reduce the risk of infecting others and said CDC is "not aware of reports that any of this individual's close contacts have developed any symptoms."

Shah also said CDC is not currently running any other confirmatory tests of H5N1. "The fact that there are not other samples cooking right now is reassuring, insofar as that we're not aware of other individuals who are symptomatic following an exposure to livestock," he said.

"We are still out there looking, to be very clear," Shah added. "Our antennae are up and we have been working with state public health officials in a number of jurisdictions to look for individuals who report signs and symptoms of illness, to make sure they know how to get tested."

Federal officials have stressed the risk to the public is currently very low, and added that commercially processed milk is still safe to drink. Dairies are required to keep milk from sick animals away from the human food supply, and any milk sold over state lines is required to be pasteurized, in which milk is heated to kill any potential pathogens. According to FDA, pasteurization "has continually proven to inactivate bacteria and viruses, like influenza, in milk."

Gail Hansen, a veterinary public health expert and independent consultant, said the risk of pasteurized milk being infected was likely "very low" and added that she "would not want people to stop drinking milk because of it." However, Hansen added the possibility couldn't be ruled out entirely.

What you need to know about bird flu

Bird flu, also known as avian influenza, is a group of viruses specifically adapted to birds. H5N1 was first identified in geese in China in 1996 and in people in Hong Kong in 1997.

By 2020, a new and highly pathogenic version of H5N1 emerged in Europe and spread around the world. It has affected more than 82 million farmed birds in the United States.

Experts note that H5N1 doesn't yet seem to have adapted to efficiently spread among people;, however, cows were not thought to be a species at risk of contracting the virus. "The fact that they are susceptible — the virus can replicate, can make them sick — that is something I wouldn't have predicted," said Richard Webby, an influenza virologist at St. Jude Children's Research Hospital.

There are a number of ways the virus could have found its way into cattle. The most likely route, according to experts, is that infected birds contaminated the cows' food or water through their feces, saliva, or other secretions.

It's possible cows are contracting the virus individually, but the U.S. Department of Agriculture said "transmission between cattle cannot be ruled out."

If the virus can easily spread between cows, this could lead to larger and more sustained outbreaks, and it would give the virus more chances to adapt to its hosts, increasing the risk it would acquire mutations that make it more dangerous to humans.

Michael Osterholm, director of the University of Minnesota's Center for Infectious Diseases Research and Policy, said the movement of the virus into cows does expand the virus's range, "but I'm not sure what it portends for humans and swine."

Osterholm said he'd be more concerned if the virus was infecting pigs, as pigs have the ability to be infected with human and avian viruses, and a co-infection of more than one type of virus in pigs can produce hybrid viruses that could more easily infect humans.

However, currently Osterholm said he believes the risk of H5N1 is not changed by its movement into cattle.

"This all could change in a heartbeat with additional mutations," he said. "But there's no evidence this virus has changed." (Anthes/Mandavilli, New York Times, 4/2; Branswell, STAT, 4/1; Sullivan, NBC News, 4/1)