Leptospirosis (Leptospira interrogans)
2013 Case Definition

Clinical Criteria

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

Clinical presentation includes history of fever within the past two weeks and at least two of the following clinical findings: myalgia, headache, jaundice, conjunctival suffusion without purulent discharge, or rash (i.e. maculopapular or petechial); OR at least one of the following clinical findings:

• Aseptic meningitis
• GI symptoms (e.g., abdominal pain, nausea, vomiting, diarrhea)
• Pulmonary complications (e.g., cough, breathlessness, hemoptysis)
• Cardiac arrhythmias, ECG abnormalities
• Renal insufficiency (e.g., anuria, oliguria)
• Hemorrhage (e.g., intestinal, pulmonary, hematuria, hematemesis)
• Jaundice with acute renal failure

Laboratory Criteria For Diagnosis

Diagnostic testing should be requested for patients in whom there is a high index of suspicion for leptospirosis, based either on signs and symptoms, or on occupational, recreational or vocational exposure to animals or environments contaminated with animal urine.

Supportive:

• Leptospira agglutination titer of ≥ 200 but < 800 by Microscopic Agglutination Test (MAT) in one or more serum specimens, or
• Demonstration of anti-Leptospira antibodies in a clinical specimen by indirect immunofluorescence, or
• Demonstration of Leptospira in a clinical specimen by darkfield microscopy, or
• Detection of IgM antibodies against Leptospira in an in acute phase serum specimen.

Confirmed:

• Isolation of Leptospira from a clinical specimen, or
• Fourfold or greater increase in Leptospira agglutination titer between acute- and convalescent-phase serum specimens studied at the same laboratory, or
• Demonstration of Leptospira in tissue by direct immunofluorescence, or
• Leptospira agglutination titer of ≥ 800 by Microscopic Agglutination Test (MAT) in one or more serum specimens, or
• Detection of pathogenic Leptospira DNA (e.g., by PCR) from a clinical specimen.

Epidemiologic Linkage

Involvement in an exposure event (e.g., adventure race, triathlon, flooding) with associated laboratory-confirmed cases.

Probable

A clinically compatible case with at least one of the following:

• Involvement in an exposure event (e.g., adventure race, triathlon, flooding) with known associated cases, or
• Presumptive laboratory findings, but without confirmatory laboratory evidence of Leptospira infection.

Confirmed

A case with confirmatory laboratory results, as listed above.

• Leptospirosis (Leptospira interrogans) | 1997 Case Definition