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Murray Valley
encephalitis (MVE) is an important mosquitoborne
flavivirus
infection
endemic to Australia and Papua New Guinea.
The Murray
Valley encephalitis virus (MVEV)
was isolated during an epidemic of encephalitis in the Murray River
valley
in Victoria and
South Australiain
in 1951. Perhaps the same virus has been isolated earlier during
epidemics of encephalitis in 1917-1918, when it went under the name of
Australian ‘X’ disease.
The primary
hosts of MVEV are water birds.
Culex annulirostris is the
primary
mosquito vector. There is no evidence of person-to-person
transmission.
MVEV can
commonly cause : Subclinical infection ; Relatively
mild disease with features such as fever, headache, nausea and
vomiting ; In some patients infected, mild disease may further
progress to involve the central nervous system, causing meningitis
; Finally there may be encephalitis of variable severity.
Signs of brain
dysfunction include drowsiness, confusion, weakness, or ataxia. These
features indicate the onset of encephalitis.
Infection is
confirmed by a significant rise in antibody titre to the virus in two
blood specimens taken seven to ten days apart.
A diagnosis of
the disease should be considered in any patient who presents with
encephalitis or central nervous system symptoms and who has been in
the endemic area within the incubation period of the disease, (usually
between November and July).
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