Asymptomatic Lyme Disease

Abstract & Commentary

Synopsis: Up to 7% of B burgdorferi infections in the United States are asymptomatic.

Source: Steere AC, et al. Asymptomatic infection with Borrelia burgdorferi. Clin Infect Dis. 2003;37:528-532.

In a study of a vaccine for prevention of lyme disease in which almost 11,000 subjects were enrolled, 269 subsequently met criteria for the infection. Of 25 patients initially classified as having asymptomatic infection from whom clinical information was subsequently available, only 15 were in fact, asymptomatic and remained so through 20 months of follow-up. Thus, only 7% of Borrelia burgdorferi infections were asymptomatic.

Comment by Stan Deresinski, MD, FACP

Prior studies have reported rates of asymptomatic seroconversion to B burgdorferi to be from 0% to 50%. Steere and associates point out that the major limitation of their analysis was that most patients with asymptomatic seroconversion received antibiotic therapy approximately 4-6 months after the tick transmission season and the subsequent follow-up was only 4-14 months. Thus, the 7% rate reported here can be considered the upper limit of the true likely incidence of asymptomatic infection. Nonetheless, the large sample size and the careful follow-up make this study a powerful one.

Dr. Derenski is Clinical Professor of Medicine, Stanford; Associate Chief of Infectious Diseases, Santa Clara Valley Medical Center.