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 behavior,” 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 behavior 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.

Hispanics make up about 15 percent of the U.S. population. They account for 18 percent of new AIDS diagnoses, according to the U.S. Centers for Disease Control and Prevention, but determining the infection rate among illegal Mexican immigrants is difficult, as many do not seek testing.

Steffanie Strathdee, a professor at the University of California, San Diego, found that residents of the border city Tijuana who injected drugs and had been deported from the United States were four times as likely to be infected with the AIDS virus as drug users who had not been deported.

New outbreaks of the virus are also being detected in small towns far from the border, researchers said.

Indigenous Zapotec migrants from the southern Mexican state of Oaxaca contracted HIV in the United States but were often too afraid of deportation to seek medical care, a joint study by Mexico’s health ministry and the California HIV/AIDS Research Program found.

If they return to their villages, they can infect their partners if they do not know, or are unwilling to reveal, that they have the disease, ministry researchers said.