Murray Valley encephalitis (MVE) virus in northern Victoria – further detections in sentinel chickens - May 2008
I wrote to you in March this year advising that Murray Valley encephalitis virus (MVE) had been detected in a sentinel chicken flock in northern Victoria. Since that time, further detections of this virus have been made in other locations in northern Victoria with the most recent detection being a week ago.
It is important that note that no human cases have been identified to date, and with the cooler weather the risk to humans is still considered low. It is however important that we remain alert to the possibility of MVE in patients who present with a compatible clinical picture, especially those who live in or have recently visited the northern part of the state.
Most cases of MVE infection are asymptomatic, while mild cases present with a febrile headache or aseptic meningitis. Symptomatic infections are usually marked by acute onset and fever commonly associated with a combination of anorexia, malaise, severe frontal headache, nausea, vomiting and dizziness. There may be progression to obvious neurological disease such as alteration in mental state, neck stiffness, ataxia and speech disturbances or convulsions. In severe cases coma, pharyngeal paralysis and respiratory failure develop.
Diagnosis depends on seroconversion demonstrated on two blood specimens separated by 7-10 days. Sera for diagnosis of human MVE infection should be sent to the Victorian Infectious Diseases Reference Laboratory (VIDRL) (ph: 03 9342 2600). In some cases MVE may also be detectable in CSF or blood using nucleic acid tests. CSF and blood for this testing should be obtained within the first few days of symptoms and referred to VIDRL.
Expert advice on case management can be obtained from the Victorian Infectious Diseases Service located at the Royal Melbourne Hospital (ph: 03 9342 7000).
Murray Valley Encephalitis is a group A notifiable disease, which means that suspected cases should be notified immediately by telephone to the Department’s Communicable Disease Prevention & Control Unit on 1300 651 160.
Thank you for your cooperation.
DR JOHN CARNIE
Chief Health Officer