By Mica Rosenberg

MEXICO CITY (Reuters) - Mexican men living and working illegally in the United States are more likely to sell their bodies for sex, take drugs or frequent prostitutes than they would have been in their homeland, increasing their risk of AIDS infection, U.S. researchers reported on Wednesday.

And if they are deported, they can take the virus back home with them, the researchers told an international conference on AIDS in Mexico City.

"They are in a new environment, they are discriminated against, they are living in harsh conditions, sometimes just in boxes covered in plastic near the farms where they work," said George Lemp of the California HIV/AIDS Research Program at the University of California, who studied 458 Mexicans before and after they left their homeland.

"When people live that way, they engage in high-risk behaviour," Lemp said in an interview.

About 11 million Mexicans live in the United States, more than half of them undocumented, and a recent U.S. crackdown on illegal immigrants and increase in deportations could make the danger of HIV infection worse, conference delegates said.

The men in the study were three times more likely to have sex with a prostitute in California than they were before leaving Mexico, Lemp's research showed. They were five times more likely to have sex while using drugs or drinking and 13 times more likely to have sex with another man.

The men were more likely to use condoms in the United States, according to the study. But their risk-taking behaviour nonetheless increases the possibility of infection, Lemp said.

In Mexico, 0.3 percent of the population is infected with HIV. In the United States, the infection rate is 0.6 percent.