One of the challenges of being a successful vertical search engine is finding that sweet spot where no one else plays. Healthline, a new health search engine out of San Francisco, thinks it’s found its spot. It’s between a general search engine such as Google and a “medical destination site” with limited content such as WebMD.

“We’re the first search engine focused on the health care domain,” said West Shell III, chairman and CEO of the company.

Healthline says its stength is the ability to interpret everyday words used by searchers and match them with medical terminology so that users can burrow down to the info they need. It does this with semantic search technology and a health taxonomy of more than 800,000 medical terms and synonyms. The company’s crawled 62,000 of the top health web sites (they have 40 million pages indexed) and hooked in with some of the top medical databases.

“Trying to search in health is an enormously difficult problem when you’ve got consumer and medical terminologies that don’t link up. It’s very tough to use a keyword type approach and get the results you’re looking for,” Shell said.

Added Vice President of Product Management Tony Gentile: “What’s different here is that if you type in arthritis, we understand that there are several different types of arthritis, and that while the average consumer will know the term arthritis, what they’re probably asking for is rheumatoid arthritis.”

There are several bells and whistles, too, including a feature called HealthMaps, which builds a visual map of the taxonomy around a person’s query, showing related terms, treatments, etc. Users can also create accounts and save pages, set up news alerts and rate and review articles. And there are doctor-reviewed articles that provide detailed overviews of medical conditions.

The company behind Healthline has actually been around for years. It started life during the tail end of the boom as YourDoctor.com, a WebMD-like site that folded during the bust. That morphed into InterMap Systems (still functioning), which is focused on enterprise health care search. Much of the health information collected over the years – and used in the enterprise product – is being leveraged for Healthline.

So far, investors have poured $24 million into the company, and the company will get another $13 milion “that should be in place in the next 30 to 60 days,” Shell says. Backers include VantagePoint Venture Partners and JHK Investments, LLC.

The business model involves paid listings and highly targeted branded advertising, as well the possibility of premium services. The company will also sell its search technology to other medical sites.

So what’s different about Healthline that will allow it to survive when so many boom-era health web sites cratered? Two things are working in the company’s favor, Gentile says. One, search sites are now our gateway to the web, thanks to Google. And two, boomers are feeling more pressure to cope with not only their own health, but that of their parents. At the same time, the financially strapped medical community has less time for hand-holding.

“If you see the doctor for a couple of minutes, it’s almost treat,” Gentile says. “So, if you want to be prepared before you see the doctor, you’re going to be looking for information. If you want to self-diagnose, you’re going to be looking for information. And if you want to understand what he or she couldn’t expain to you, you’re coming to a search engine.”