Another factor bolstering the conclusion of reinfection rather than relapse was the timing of second infections -- in 20 of the 22 cases, they occurred from June through August, when the ticks responsible for transmitting B. burgdorferi are most active in the New York area.
Also, the time between episodes was never less than 1 year and ranged up to 15 years. Nadelman and colleagues cited earlier research suggesting that, in cases of antibiotic failure, relapses occur within days to weeks.
In an accompanying editorial, Dr. Allen C. Steere of Massachusetts General Hospital in Boston, said the new study supports the conclusion that current antibiotic treatments are adequate to eliminate Lyme infections.
As a result, he suggested, reinfection is the best explanation when erythema migrans lesions are detected again after treatment.
"The issue of relapse versus reinfection has a broader context because of patient-advocacy groups that promote months or years of antibiotic therapy for 'chronic Lyme disease,'" Steere added.
Many patients and some physicians believe that B. burgdorferi can persist after antibiotic treatment and also evade detection with molecular and serological tests, producing long-term symptoms such as diffuse pain and fatigue. According to this theory, months or years of antibiotic therapy may be needed to manage the condition.
Although this theory has been soundly rejected by mainstream organizations such as the Infectious Diseases Society of America, a vocal movement continues to advocate it.
But Steere indicated that the current study is more evidence that the chronic-Lyme theory is false.
"Although B. burgdorferi infection may persist for years in untreated patients, the weight of evidence is strongly against persistent infection as the explanation for persistent symptoms in antibiotic-treated patients with Lyme disease," he wrote.