Mar 1, 2004 12:00 PM

A highly contagious strain of avian flu found on a chicken farm in South Texas is much more dangerous to poultry than originally thought and has spread to markets in Houston, according to federal officials.

The flu strain, found in Gonzales County about 50 miles east of San Antonio, is no real threat to humans, said Dr Nancy Cox of the Centers for Disease Control and Prevention. It is not the same strain that has killed at least 22 people in Asia, said Dr Ron DeHaven of the United States Department of Agriculture.

This marks the first instance since 1983-84 of high-pathogenic avian flu in the United States, said DeHaven.

The Texas farm's flock of 6,600 birds has been destroyed, though chickens from that flock already had been shipped to two live-bird markets in Houston.

According to preliminary tests, the flu was detected in the live-bird markets, DeHaven said. Birds at one of the markets also were destroyed, and the same process had begun at the other location, he said.