HOUSTON -- While there are concerns that the bird flu could travel overseas to the United States, a subtype of the bird flu appeared in Texas last year, KPRC Local 2 reported Thursday. It cost millions of dollars and thousands of birds' lives.

At a Houston bird market, live chickens are bought by people looking to prepare a fresh meal. Last year, birds from two of Houston's live bird markets tested positive for the avian flu.

"All the birds were depopulated and the facilities were cleaned and disinfected," said Max Coats, with the Texas Animal Health Commission.

Coats and his colleagues traced the infected birds back to a chicken farm in Gonzales, Texas. The farm was immediately quarantined. The flock was killed and the state set up a task force to prevent a possible outbreak of bird flu.

"Because these flu viruses, if left alone, they do change themselves," Coats said.

The virus killed 50,000 chickens and caused 40 countries to ban poultry and egg products from Texas.

A major outbreak in Texas and the U.S. was successfully avoided. The state said that it was due in part to its strict "Avian Influenza" plan.

"Our standard response is to test anything in a 10-mile radius. That's what all the circles are about," Coats said.

Their response also included telling poultry exhibitors at rodeo and livestock shows to pull their birds. That is because the virus can easily be passed with the help of humans. Just one gram of manure on a boot, clothing or piece of equipment can contain enough of the virus to infect a million birds.

"We never let our guard down," Coats said.

At a lab in College Station, Dr. Lev Gayle and his colleagues have been testing for the bird flu since the early 1990s when an outbreak in Mexico caused a scare.

"We're taking in samples and running tests 24-7, 365 days a year," Gayle said.

The lab detected the deadly virus that hit Texas last year. It was identified as a different subtype of the Asian bird flu or virus being blamed for human deaths in Asia.

Although there has never been a reported human case of the bird flu virus here, scientists admit it could happen because of the virus' uncanny ability to mutate and adapt.

"It's like a question of time that it does come up with a form that does affect humans," Gayle said. "In biology I would hate to never say never."

This month, the killer 1918 pandemic was discovered to have been caused by a bird flu that jumped to humans and then developed the ability to be passed from person to person. The question now is could that happen to the Asian flu or with the bird flu strains that hit Texas last year.

"Everything can happen once," Gayle said. "This outbreak, if it happens, is not going to happen on Plum Island. It's not going to be up in New York. It's going to be in a feed lot in Amarillo."

Scientists in Texas say they are more than prepared to deal with an outbreak.

The Texas Poultry Federation has all its members regularly test their flocks for the avian flu. Last year's bird flu was detected through this routine monitoring.

All poultry owners are encouraged to call the state if they see any signs that their birds are sick or dying. The number to call is (800) 550-2966.