A US pornographic film actress is the fifth person to test positive for the HIV virus in an outbreak which has halted most work in the industry.
The California-based porn industry is worth billions of dollars a year
The new case involves an industry veteran, one of up to 14 people believed to have been infected during on-camera sex with a male actor.
He is thought to have been infected while working in Brazil.
About 50 people connected through their work to the actor are on a voluntary quarantine list.
The California-based porn industry generates billions of dollars of income a year.
About 200 production companies are said to make 4,000 films a year for public viewing, using about 1,200 performers.
More than 1,000 actors are tested for HIV every three weeks by the Adult Industry Medical Healthcare Foundation (Aim).
The foundation's goal is for performers to be tested every 30 days for the disease.
Sharon Mitchell, a former porn actress who now runs Aim, said the male actor had passed the virus to at least three co-stars.
The woman whose positive test has just been revealed was one of about 50 performers under a 60-day quarantine because they had had direct or indirect contact with the actor, Ms Mitchell said.
Last month, health officials in California said the infections meant they may force performers to use condoms.
Los Angeles County officials said they believed existing regulations gave them the authority to require the use condoms, which can reduce the risk of the disease being passed on.
Analysts have warned that most porn producers and distributors would not switch to condom-only productions as consumers do not like to see them being used in films.
But a number of companies joined a two-month shutdown.
Correspondents say the timing of the scare is unfortunate as the US is in the midst of a debate over taste and decency in the media which could become an election issue.
The porn industry will not want to draw more attention from politicians keen to advocate greater regulation of its activities, they say.