Skip directly to search Skip directly to A to Z list Skip directly to navigation Skip directly to page options Skip directly to site content

Leptospirosis (Leptospira interrogans)
1997 Case Definition

Clinical Description

An illness characterized by fever, headache, chills, myalgia, conjunctival suffusion, and less frequently by meningitis, rash, jaundice, or renal insufficiency. Symptoms may be biphasic.

Laboratory Criteria for Diagnosis

  • Isolation of Leptospira from a clinical specimen, OR
  • Fourfold or greater increase in Leptospira agglutination titer between acute- and convalescent-phase serum specimens obtained greater than or equal to 2 weeks apart and studied at the same laboratory, OR
  • Demonstration of Leptospira in a clinical specimen by immunofluorescence

Case Classification


A clinically compatible case with supportive serologic findings (i.e., a Leptospira agglutination titer of greater than or equal to 200 in one or more serum specimens)


A clinically compatible case that is laboratory confirmed


The 1997 case definition appearing on this page was previously published in the 1990 MMWR Recommendations and Reports titled Case Definitions for Public Health Surveillance.1 Thus, the 1990 and 1997 versions of the case definition are identical.


  1. CDC. (1990). Case Definitions for Public Health Surveillance. MMWR, 39(RR-13), 1-43.