WALNUT CREEK, Calif. - Politicians do it. So do celebrities. Now doctors and health-care organizations are doing it: using Twitter to promote health, provide swine flu updates, and capsulize the latest research findings. Many believe Twitter will be an especially valuable tool in a public-health emergency.

"It gives us access to a huge audience," said Kate Fowlie, communications officer for Contra Costa Health Services in California. "A lot of people use it, so we need to be there so we can make sure that our information gets heard."

Twitter's adoption in the health-care field demonstrates how it is evolving from entirely frivolous postings, or tweets, to some serious content.

Twitter, the free social networking service, allows users tweets of no more than 140 characters; they are snippets of information meant to be read quickly from a computer or cell phone.

Many health professionals began thinking about using Twitter when the swine flu outbreak hit in April.

Rahul Parikh, a pediatrician at Kaiser Permanente, decided Twitter would enable him to point his patients to reliable information so "they wouldn't get worried unnecessarily." He sent them links to Web articles about swine flu that he found enlightening, informed them of Kaiser flu clinics, and let them know when he'd be out of the office.

Because of privacy concerns, Parikh has told his patients not to tweet him with personal medical questions, which he said are best handled through private e-mails.

Parikh believes Twitter can help empower patients to make better decisions about their health care. He has posted links to information about such topics as sunscreen; bathtub accidents, which injure 43,000 children a year; and medical myths.

"My goal is to try and find ways to make health care more accessible to patients," he said. "This is one way to do that."

Contra Costa Health Services also began using Twitter when swine flu emerged. Communications officer Fowlie updated the number of deaths and confirmed cases, school closings, and tips on how to avoid getting sick. She continues to tweet regularly for the department's 312 followers.

She recently posted details on immunization clinics, tips on dealing with stress, and ways to avoid heat exhaustion.

For those who use Twitter, "it raises people's consciousness about what's happening," she said. "We've integrated it into our overall communication strategy."

Others using Twitter to provide breaking health information include Mark Horton, director of the California Department of Public Health, the national Centers for Disease Control and Prevention, and the World Health Organization.

"With so many people turning to the Internet with health questions, selecting a few trusted agencies or experts to follow on Twitter can be one way to help ensure that information is reliable," Parikh said.