Murray Valley encephalitis virus infection case definition

This document contains the case definitions for Murray Valley encephalitis virus infection which is nationally notifiable within Australia. This definition should be used to determine whether a case should be notified.

Page last updated: 01 July 2010

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1.1

Change all references to Kunjin on lines 15 and 18 to West Nile virus/Kunjin.

Change the numbering under clinical evidence, number 2. is to be replaced with a number 3.

CDWG 4 November 2009

CDNA 12 May 2010

1 July 2010

1.0 Initial case definition (2004)      

Reporting

Only confirmed cases should be notified.

Confirmed case

A confirmed case requires Laboratory definitive evidence AND clinical evidence.

Laboratory definitive evidence

1. Isolation of Murray Valley encephalitis virus

OR

2. Detection of Murray Valley encephalitis virus by nucleic acid testing

OR

3. IgG seroconversion or a significant increase in antibody level or a fourfold or greater rise in titre to Murray Valley encephalitis virus

OR

4. Detection of Murray Valley encephalitis virus-specific IgM in cerebrospinal fluid in the absence of IgM to West Nile/Kunjin, Japanese encephalitis and dengue viruses

OR

5. Detection of Murray Valley encephalitis virus-specific IgM in serum in the absence of IgM to
West Nile/Kunjin, Japanese encephalitis and dengue viruses. This is only accepted as laboratory evidence for encephalitic illnesses.

Confirmation of laboratory result by a second arbovirus reference laboratory is required if the case occurs in areas of Australia not known to have established enzootic/endemic activity or regular epidemic activity.

Clinical evidence

1. Non-encephalitic disease: acute febrile illness with headache, myalgia and/or rash

OR

2. Encephalitic disease: acute febrile meningoencephalitis characterised by one or more of the following:

  • focal neurological disease or clearly impaired level of consciousness
  • an abnormal computerised tomograph or magnetic resonance image or electroencephalogram
  • presence of pleocytosis in cerebrospinal fluid

OR

3. Asymptomatic disease: case detected as part of a serosurvey should not be notified.

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