Flavivirus infection (unspecified) case definition

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

Communicable Diseases Surveillance

Australian national notifiable diseases case definitions - Flavivirus infection (unspecified)

Note

1. It is recognised that some cases of human infection cannot be attributed to a single flavivirus. This may either be because the serology shows specific antibody to more than one virus, specific antibody cannot be assigned based on the tests available in Australian reference laboratories, or a flavivirus is detected that cannot be identified.

2. Confirmation by a second arbovirus reference laboratory is required if the case cannot be attributed to know flaviviruses.

3. Occasional human infections occur due to other known flaviviruses, such as Kokobera, Alfuy, Edge Hill and Stratford viruses.

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 a flavivirus that cannot be identified in Australian reference laboratories or which is identified as one of the flaviviruses not otherwise classified

2. Detection of a flavivirus, by nucleic acid testing, that cannot be identified in Australian reference laboratories or which is identified as one of the flaviviruses not otherwise classified

3. IgG seroconversion or a significant increase in antibody level or a fourfold or greater rise in titre of flavivirus specific IgG that cannot be identified or which is identified as being specific for one of the flaviviruses not otherwise classified. There must be no history of recent Japanese encephalitis or yellow fever vaccination

4. Detection of flavivirus IgM in cerebrospinal fluid, with reactivity to more than one flavivirus antigen (Murray Valley encephalitis, Kunjin, Japanese Encephalitis and/or dengue) or with reactivity only to one or more of the flaviviruses not otherwise classified

5. Detection of flavivirus IgM in the serum, with reactivity to more than one flavivirus antigen (Murray Valley encephalitis, Kunjin, Japanese Encephalitis and/or dengue) or with reactivity only to one or more of the flaviviruses not otherwise classified. This is only accepted as laboratory evidence for encephalitic illnesses. There must be no history of recent Japanese encephalitis or yellow fever vaccination

Clinical evidence

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

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 electrocardiograph

• presence of pleocytosis in cerebrospinal fluid.