Lyme Disease.

Lyme disease, or borreliosis, is an emerging infectious disease caused by at least three species of bacteria belonging to the genus Borrelia. Borrelia burgdorferi is the predominant cause of Lyme disease in the United States, whereas Borrelia afzelii and Borrelia garinii are implicated in most European cases.
Lyme disease is the most common tick-borne disease in the Northern Hemisphere. Borrelia is transmitted to humans by the bite of infected hard ticks belonging to several species of the genus Ixodes. Early manifestations of infection may include fever, headache, fatigue, depression, and a characteristic skin rash called erythema migrans. Left untreated, late manifestations involving the joints, heart, and nervous system can occur. In a majority of cases, symptoms can be eliminated with antibiotics, especially if diagnosis and treatment occur early in the course of illness. Late, delayed, or inadequate treatment can lead to late manifestations of Lyme disease which can be disabling and difficult to treat.
Some groups have argued that "chronic" Lyme disease is responsible for a range of medically unexplained symptoms beyond the objectively recognized manifestations of late Lyme disease, and that long-term antibiotic treatment is warranted in such cases. However, a series of randomized controlled trials found no significant benefit from prolonged antibiotic treatment in such patients, and most expert groups including the Infectious Diseases Society of America and the American Academy of Neurology have found that existing scientific evidence does not support a role for Borrelia nor ongoing antibiotic treatment in such cases