Measles case definition

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

Page last updated: 29 May 2019

Version Summary of changes Last reviewed Implementation date
1.0

Initial case definition

2004 2004
1.1
  • Additional detail to laboratory definitive evidence point 4 criterion and inclusion of a footnote to allow recently vaccinated cases to potentially be considered as confirmed cases
  • IgM antibody detection adjusted and moved from laboratory definitive evidence to laboratory suggestive evidence
  • Additional detail to epidemiological evidence including contact for infectious period changed from five days before rash onset to 24 hours before onset of prodromal symptoms or four days before rash onset
15 May 2019 1 July 2019

Reporting

Both confirmed cases and probable cases should be notified.

Confirmed case

A confirmed case requires either:

  1. laboratory definitive evidence

OR

  1. clinical evidence AND epidemiological evidence.*

Laboratory definitive evidence

At least one of the following:

  1. Isolation of measles virus*

OR

  1. Detection of measles virus by nucleic acid testing*

OR

  1. Detection of measles virus antigen*

OR

  1. IgG seroconversion or a significant increase in antibody level, such as a fourfold or greater rise in titre to measles virus EXCEPT if the case has received a measles-containing vaccine eight days to eight weeks prior to convalescent specimen collection. (NOTE: paired sera must be tested in parallel).

*Where measles vaccine has been given in the three weeks prior to illness onset and wild-type virus is not detected, or unable to be detected, a case may be considered “confirmed” only if the criteria for clinical and epidemiological evidence can also be met, suggesting wild-type infection. Vaccine-associated measles illness (genotype A) is not notifiable, but rather should be reported as an adverse event following immunisation.

Clinical evidence

An illness characterised by all of the following:

  1. A generalised maculopapular rash lasting three or more days

AND

  1. Fever (at least 38 C if measured) at the time of rash onset

AND

  1. Cough OR coryza OR conjunctivitis OR Koplik spots.

Epidemiological evidence

An epidemiological link is established when there is:

  1. Contact between two people involving a plausible mode of transmission at a time when:
    1. one of them is likely to be infectious (from 24 hours before onset of prodromal symptoms or four days before rash onset to four days after rash onset)

AND

  1. the other has an illness that starts within seven to 18 days after this contact

AND

  1. At least one case in the chain of epidemiologically linked cases (which may involve many cases) has laboratory confirmed measles.

Probable case

A probable case requires laboratory suggestive evidence AND clinical evidence.

Laboratory suggestive evidence

Detection of measles specific IgM antibody; EXCEPT

  1. If ruled out by more specific measles IgM serology testing at a jurisdictional public health laboratory, OR
  2. If the case has received a measles-containing vaccine eight days to eight weeks before testing.

Clinical evidence

As with confirmed case.

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