Early Lyme disease: a flu-like illness without erythema migrans.

The existence of a form of early Lyme disease characterized by a flu-like illness without erythema migrans is controversial. To confirm the existence and define the clinical characteristics of the flu-like illness without erythema migrans of localized Lyme disease, the authors studied patients from a Lyme disease endemic area of Connecticut who visited their primary care physicians with an undefined flu-like illness. Patients kept a diary of their symptoms. Acute and convalescent sera were obtained. The diagnosis of Lyme disease was based on the appearance of IgM or IgG antibodies to Borrelia burgdorferi as demonstrated by both enzyme-linked immunosorbent assay and immunoblot assay. Twenty-four untreated patients were studied. In five patients acute serologic evidence of Lyme disease developed. The flu-like illness in these five patients was characterized by fever and fatigue and resolved spontaneously in 5 to 21 days. Symptoms recurred in three of these five patients. The existence of a flu-like illness without erythema migrans of early Lyme disease has been clearly established. Prospective, controlled studies are needed to better define its incidence, characteristics, and prognosis so that appropriate diagnostic and therapeutic strategies can be developed.