Leptospira is a type (genus) of elongated, spiral-shaped bacteria. Infection can cause Weil's disease, a kind of jaundice, in humans. Leptospira is a genus of spirochaete bacteria, including a small number of pathogenic and saprophytic species. Leptospira was first observed in 1907 in kidney tissue slices of a leptospirosis victim who was described as having died of yellow fever. Leptospira, together with the genera Leptonema and Turneria, is a member of the family Leptospiraceae. The genus Leptospira is divided into 20 species based on DNA hybridization studies. Leptospira have a Gram-negative-like cell envelope consisting of a cytoplasmic and outer membrane.