How a louse-borne pathogen evades the immune system

Louse-borne relapsing fever is caused by the spirochete bacterium Borrelia recurrentis, which is transmitted by body lice (not head lice). The disease was first described by Hippocrates (460–370 B.C.). Initial symptoms include a high fever lasting several days, followed by a fever-free interval. Typically, several recurrent episodes of fever follow. The disease can be treated with antibiotics. If left untreated, however, infection with Borrelia recurrentis is fatal in up to 20% of cases—particularly in regions where comprehensive medical care is not available.