LOS ANGELES (Reuters) - You've got mail -- and possibly gonorrhea, HIV or another sexually transmitted disease.

E-mail sent through Web sites launched in Los Angeles and San Francisco is providing people with a free, sometimes anonymous, way to tell their casual sex partners they might have picked up more than they bargained for.

Los Angeles County health officials launched www.inspotla.org this week in a bid to reduce the rapidly rising spread of STDs by encouraging sexually active men and women to get tested.

"This is another opportunity for people to disclose STD exposure to partners because sometimes people don't always have that face-to-face opportunity, or that level of relationship," Karen Mall, director of prevention and testing at the AIDS Healthcare Foundation, said on Thursday.

"Partner disclosure is where we really have the opportunity to break the chain of HIV infection," Mall said.

The site allows users to choose one of six free e-cards to send to their sexual contacts either unsigned or with a personal message that avoids awkward face-to-face disclosure.

"It's not what you bought to the party, it's what you left with," says one e-card featuring a picture of a bare-chested man. "I left with an STD. You might have one too. Get checked out soon."

"You're too hot to be out of action," says another.

The Los Angeles Gay and Lesbian Center, which runs its own counseling services for partner disclosure, welcomed the Web site program.

"Many of the people we are seeing are listing the Internet as the place where they are meeting partners, so the Web site is a really helpful tool for prevention and contacting them," said Tiffany Horton, manager of the center's sexual health program.

The site is modeled on one launched in San Francisco last year (www.inspot.org) that is generating about 500 e-cards a month. Both are targeted at gay men but can be used by anyone.

Health officials call the e-cards a "fast, free and flexible partner notification system" that also gives information and links to local testing sites.

Some 2,400 new AIDS cases were reported in Los Angeles County in 2003, along with more than 8,000 new gonorrhea cases and 830 new syphilis cases -- most of them among gay men.

The Web sites urge users to show respect and not to misuse the system. Mall said only half of 1 percent of the e-cards sent through the San Francisco site had been malicious or fraudulent.

"The sites do not give anybody the ability to do anything they can do already if they had somebody's e-mail," Mall said.

"It is something we can monitor. People can get hold of the Web master if they have concerns or want to complain.

"But I give the (gay) community more credit than that. I think the community really wants to get ahead of HIV and STDs and they realize that notification is really important," she said.

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