President Bush's recently revealed treatment for Lyme disease makes him part of an unfortunate trend: The tick-borne infection is on the rise, with cases more than doubling in the past 15 years.

The good news is that most patients, like Bush, take antibiotics for a few weeks and are cured, especially if they were diagnosed early.

But people who aren't treated promptly can develop painful arthritis, meningitis and other serious illnesses. If they don't experience, or notice, Lyme's hallmark round, red rash, they can struggle to be diagnosed, as other early symptoms are flu-like and vague.

And a small fraction of patients report pain and fatigue that linger for months or years after treatment. Do they still have Lyme, or something else? No one knows, although desperate patients often try repeated antibiotics despite little evidence that the drugs do more good than harm.

The central problem: No test can tell when someone has active Lyme disease — when Lyme-causing bacteria are alive in the body. Today's tests instead spot infection-fighting antibodies, which can take weeks to form but then linger long after Lyme is gone.

A push is on for better Lyme tests, with parallel hunts getting started by the National Institutes of Health and, separately, by patient advocacy groups angry that modern medicine hasn't found an answer.

"The time is right to take a closer look," says Dr. Dennis M. Dixon, chief of bacteria research at the NIH's National Institute for Allergy and Infectious Diseases, which plans to gather leading scientists later this year to determine the best approaches. "We would not rule out any avenue."

"We have a lot of new tools" to explore, adds Dr. Brian Fallon, who directs Columbia University's new Lyme and Tick-borne Diseases Research Center, funded by the advocacy groups Time for Lyme and the Lyme Disease Association. "Science is going to bridge the gap."

Among the research:

—A newer antibody test seems to indicate when antibiotics are working in early Lyme stages, offering the possibility of tracking treatment response.

—Hunting markers of active infection, including bits of Lyme-related protein in the blood or spinal fluid.

—Fallon is using brain imaging to try to distinguish when Lyme penetrates the nervous system.

About 20,000 new cases of Lyme disease are reported to the government every year, says a June analysis from the Centers for Disease Control and Prevention.

The CDC acknowledges that's a fraction of the true toll, as many cases go unreported. Experts say it may be five times higher.

Still, the figure is more than double the count in 1991, when official tracking began, and CDC says it's not due just to better awareness of Lyme. The rise is expected to continue as suburbia expands into the woodland home of black-legged tick species, commonly called deer ticks, that carry Lyme-causing "Borrelia burgdorferi" bacteria in the Northeast, mid-Atlantic, north-central states and Pacific Coast.

The only human vaccine was pulled off the market in 2002 for lack of consumer interest. It was partly protective; better, next-generation vaccines are years away.

Don't live in a high-Lyme area? Different tick species carry different threats, such as Rocky Mountain spotted fever. Most recently discovered is STARI, or Southern tick-associated rash illness — a rash very similar to Lyme's but not yet linked to other symptoms. It's caused by a still unknown organism carried by the lone star tick.

But Lyme is the most common tick-borne infection, and overshadowing the treatment success for most patients is debate over what patient groups call "chronic Lyme" and mainstream medicine, striving for neutrality, calls "post-Lyme syndrome."

The two camps became even more polarized as two major medical associations released guidelines in the past year that found no good evidence that long-term antibiotics help lingering symptoms — but warned they can cause serious side effects and spur formation of drug-resistant super-germs.

"If there were evidence that prolonged therapy was beneficial ... I'd be the first person to jump on the bandwagon," says Dr. Eugene Shapiro, a Yale University pediatrics professor and co-author of the guidelines from the Infectious Diseases Society of America and American Academy of Neurology.

That's not to say some people aren't sick, the guidelines stress, just that it's not clear why. Among other possibilities, Lyme may over-activate some people's immune systems so that antibodies attack their own joints.

"I think many have been told they have Lyme when in fact they have something else," says Dr. Paul Auwaerter, an infectious disease specialist at Johns Hopkins University. "I can sense, palpably, their frustration."

Furious patient groups say the guidelines prompted some insurers to quit paying for some patients' only relief — and that the recommendation instead should have been there's not enough data to know what works. Diane Blanchard, co-president of Time for Lyme, points insurers to still other guidelines, from the International Lyme and Associated Diseases Society, doctors aligned with the patient groups who back more antibiotics.

"The last thing many of us want to do is ingest an antibiotic," says Blanchard. "We are basically sitting on our hands watching this disease expand its ill effect ... and doing very little except for taking sides, and essentially that's not helping anyone."