A Canadian teen working in the American porn industry has been found HIV positive, prompting adult movie companies to stop production and bar some performers from the set.

Both the 19-year-old Canadian woman and a male actor have the disease, and at least 45 other actors are in voluntary quarantine. Several are getting tested.

It's believed the male actor got the virus while shooting in Brazil, then passed it on to the Canadian actress. Her identity has not been released. An industry news magazine, AVN, said the woman had only been working in the porn industry for three months.

Industry experts said about a dozen companies have agreed to stop production voluntary for a two-month moratorium while more tests for the virus are completed.

Dr. Jonathan Fielding, director of public health for Los Angeles County, said news of the infections show that screening programs aren't foolproof. The only way to avoid getting the virus "is not to have unprotected sex," he told The Associated Press.

There have been a few HIV scares in the porn industry. In 1999, a male actor tested positive, but no other actors were infected. He no longer performs. In 1998, another male actor with the virus infected five women.

A health group is working to identify performers who worked with the infected actors, and any others who may have been exposed to the virus through secondary contact.

The American porn industry makes billions of dollars a year. It's based in the San Fernando Valley and produces about 4,000 films a year.