On a date in Manhattan and need protection? There's an app for that -- sponsored by the New York City Department of Health and powered by GPS, it guides users to nearby locations with free condoms.

Need AIDS advice in Spanish? The Centers for Disease Control and Prevention has a Twitter handle in Spanish with almost 25,000 followers (@CDCEspanol).

As sexually active young adults move their romantic life out of nightclubs and onto the Internet, public health leaders are following with creative strategies.

"When something goes viral, you've reached millions of people in a day,'' said Simon Rosser, a University of Minnesota researcher who is one of several scholars making presentations on social media at the International AIDS Conference in Washington, D.C., this week.

Tools such as YouTube and Google+ can reach huge audiences with basic information on testing, symptoms and safe-sex techniques. Facebook and Twitter allow people without computers to participate through mobile devices, notes Tina Hoff, a spokeswoman at the Kaiser Family Foundation.

Public health officials acknowledge that social media are only part of the many tools in the battle to contain HIV. They say social media should not replace personal advice from a doctor or nurse, for example.

Such methods also require a level of comfort with sharing private information online.

"Most forms of social media are not entirely anonymous,'' Hoff wrote. "To talk about HIV on Twitter or Facebook would be a much more public forum than at a local ... clinic."

At the same time, social media can reach people who lack access to care because of geographic, financial or cultural barriers. It also allows highly tailored information.

The Minnesota AIDS Project (MAP), for example, uses Twitter, Facebook and texts to alert people where volunteers will be distributing safe-sex kits. The Bill and Melinda Gates Foundation, which funds AIDS research and global relief work, has almost 800,000 followers on Twitter.

In Minnesota, the conversation takes place through programs like MAP's 10,000 Messages and HIV Action Network, and the Health Department is accepting grant applications for community programs that use social media.

"That's the way people connect and communicate,'' said Peter Carr, manager of the department's STD and HIV Section. "We need to be in touch with that.''