In this peripheral blood smear can be seen several small corkscrew-shaped organsisms of Borrelia recurrentis. This patient presented with shaking chills, fever, and headache. Her D-dimer was elevated. The antigenic variation of this infectious agent provides a means for escaping antibody-mediated destruction temporarily, allowing for relapse with growth of numerous organsisms that can be seen on the peripheral blood smear. So many organisms are present that antibiotic therapy can produce massive endotoxin release (Jarisch-Herxheimer reaction). Borreliosis is a tick and louse-borne infection. The spirochete that causes Lyme disease, Borrelia burgdorferi, has a similar morphology, but relatively few organisms are present, and the host immune response that produces the major manifestations of Lyme disease is out of proportion to the small numbers of organsisms present.