Leptospirosis case definition

This document contains the case definitions for Leptospirosis which is nationally notifiable within Australia. This definition should be used to determine whether a case should be notified.

Page last updated: 19 December 2021

Surveillance case definition

Version Summary of changes Last reviewed Implementation date
2.0 Inclusion of a probable category for cases with laboratory suggestive evidence. November 2021

01 January 2022
1.0 Initial case definition 2004 2004

Australian national notifiable diseases case definitions – Leptospirosis


Both confirmed cases and probable cases should be notified.


Confirmed case

A confirmed case requires laboratory definitive evidence only.

Laboratory definitive evidence

  1. 1. Isolation of pathogenic Leptospira species


  1. A fourfold or greater rise in Leptospira agglutination titre between acute and convalescent phase sera obtained at least two weeks apart and preferably conducted at the same laboratory


  1. A single Leptospira micro agglutination titre greater than or equal to 400 supported by a positive enzyme-linked immunosorbent assay IgM result.

Probable case

A probable case requires laboratory suggestive evidence.

Laboratory suggestive evidence

Detection of pathogenic Leptospira species by nucleic acid testing.

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