When people who have been treated for Lyme disease recover but later come down with its symptoms again, is the illness a relapse or a new infection?
The question has lingered for years. Now, a new study finds that repeat symptoms are from new infections, not from relapses.
The results challenge the notion, strongly held by some patients and advocacy groups, that Lyme disease, a bacterial infection, has a tendency to resist the usual antibiotic treatment and turn into a chronic illness that requires months or even years of antibiotic therapy.
The conclusion that new symptoms come from new infections is based on genetically fingerprinting the Lyme bacteria in people who have had the illness more than once, and finding that the fingerprints do not match. The result means that different episodes of Lyme in each patient were caused by different strains of the bacteria, and could not have been relapses.
The study, by researchers at the University of Pennsylvania and New York Medical College, in Valhalla, was published online on Wednesday in The New England Journal of Medicine.
An estimated 20,000 to 30,000 cases of Lyme disease occur each year in the United States. The disease is caused by a bacterium, Borrelia burgdorferi, that is carried by deer ticks. It often begins with an expanding zone of red skin — a symptom called erythema migrans — around the tick bite, but sometimes in other areas too. Fever, headaches, fatigue and aches and pains often follow.
Untreated, the disease can cause heart and neurological problems and arthritis, with symptoms that can come and go for years. Advanced cases that have gone months or years before being treated are most likely to result in persistent arthritis.
But when the disease is detected earlier, treatment with an antibiotic, usually two to four weeks of doxycycline, can get rid of the bacteria, according to infectious disease experts. Even advanced cases can be cleared by the drugs, doctors say, though an extra month or so of treatment may be needed. Symptoms like pain and fatigue can linger even after the bacteria are gone, possibly because the infection caused abnormalities in the immune system.