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/ Source: TODAY
By Linda Carroll

Avril Lavigne’s recent diagnosis of Lyme disease is a reminder to how difficult it can be to detect the tick-borne illness.

Lavigne suffered from a crushing fatigue for months before doctors finally figured out what was wrong.

“I had no idea a bug bite could do this,” Lavigne told People magazine. “I was bedridden for five months. There were times I couldn’t shower for a full week because I could barely stand. It felt like having all your life sucked out of you.”

Lyme disease is caused by a bacterium carried and transmitted by deer ticks, which are so tiny that people often don’t even see them, so they don’t know they’ve been bitten. The bacterium, Borrelia burgdorferi, is closely related to the one that causes syphilis—both are spirochetes, so named because of their corkscrew appearance.

Although some 70 percent of people infected with the Lyme bacterium develop a red rash after their tick bite, a sizable minority do not, says Dr. Anne Norris, an assistant professor of clinical medicine at the University of Pennsylvania School of Medicine.

Those folks will often have a prolonged fever that doesn’t seem to be connected with a head cold or stomach bug, Norris says. They may also suffer from aching muscles.

“They feel pretty sick,” she adds.

But not everyone who suffers from these symptoms will have Lyme disease, Norris adds. There is a blood test, but doctors don't always think to screen for Lyme unless the patient is in an area where the disease is common. The test results can also be challenging to interpret, depending on how recently someone has been bitten by a tick, Norris says.

Untreated, Lyme disease can lead to severe neurological symptoms.

For areas where Lyme is endemic, like the Northeast, “it’s something you clearly need to think about even if you don’t remember a tick bite,” says Dr. Scott Curry, a clinical assistant professor in infectious diseases at the University of Pittsburgh School of Medicine. “On the other hand if you live in a place like New Mexico and you haven’t traveled then it becomes almost a zero possibility.”

Initial symptoms can be very flu-like, he says, adding that the disease can be successfully treated with antibiotics. But that doesn’t mean you can’t be reinfected, he adds.

People who spend a lot of time outdoors—landscapers, hunters, fishermen, for example—need to be on the lookout for rashes because they can get Lyme more than once, Curry says.

When a patient calls in with a rash he’ll ask them to shoot a photo with their phone and send it to him.

“If the rash looks Lyme-y, then they need another round of antibiotics,” Curry says.

In Lavigne’s case, the correct diagnosis has meant a return to her former self. “I’m about 80 percent better,” she told People.

Linda Carroll is a regular contributor to NBCNews.com and TODAY.com. She is co-author of "The Concussion Crisis: Anatomy of a Silent Epidemic” and the recently published “Duel for the Crown: Affirmed, Alydar, and Racing’s Greatest Rivalry