NOTE: A surveillance case definition is a set of uniform criteria used to define a disease for public health surveillance. Surveillance case definitions enable public health officials to classify and count cases consistently across reporting jurisdictions. Surveillance case definitions are not intended to be used by healthcare providers for making a clinical diagnosis or determining how to meet an individual patient’s health needs.

CSTE Position Statement(s)

  • 18-ID-16

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.

Related Case Definition(s)

Page last reviewed: April 16, 2021