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Murray Valley Encephalitis:
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Viral weapon acting on humans |
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Synopsis,Diagnosis, Symptoms,
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Safety Precautions for Casualties |
Standard Precautions defined by the 1996 CDC guidelines should be adopted for handling patients.Mosquito control should be practiced.Biosafety level 3 practices should be adopted for handling of samples. |
| Causative organism: (Systematic name in 1997) | Murray Valley encephalitis virus |
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| ICTV Acronym | MVEV |
| Properties: |
Click here for a detailed description of Flaviviruses |
| Alternative disease names: |
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| Vector Involvement: | The disease is carried by culicine
mosquitoes especially of the genus Culex. Culex annulirostris is the key vector in transmission to man and other species play a role in transmission among animal reservoirs. |
In most cases, the infection is subclinical or relatively mild, including, fever, headache, nausea and vomiting.
In severe cases, the central nervous system becomes involved with symptoms ranging from meningitis to an encephalitis including drowsiness, confusion, convulsions, weakness, and ataxia.
Differential DiagnosisOther disease or conditions that need to be eliminated |
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| Other infectious diseases | Other problems |
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Symptoms and effects.
Infection with Murray Valley encephalitis is often subclinical and perhaps only 1 in 800-1000 or more of those infected will go on to develop a clinically significant disease. For everyone else, the symptoms can range from mild to severe. The incubation period is 7-28 days and symptoms almost invariably include fever; headache nausea and vomiting are common. Of those who show clinically significant disease, 25% have died and 25-50% show permanent neurological damage.
When an encephalitis develops, brain dysfunction may be experienced after a few days with lethargy, irritability, drowsiness, confusion, convulsions and fits; neck stiffness can be expected, and both coma and death may ensue.
Medical and Physical Countermeasures.
Vaccination (Immunoprophylaxis)
No vaccine is available.
Specific Therapy
None, treatment is symptomatic.
Supportive care
The virus is killed by heat and is susceptible to common disinfectants; 70% ethanol, 1% sodium hypochlorite, 2% glutaraldehyde.
Agent Properties and Potential Uses
Murray Valley encephalitis is established in northern and western Australia and has also been seen in New Guinea and Indonesia. Significant outbreaks have followed major flooding rains in the area. The last major outbreak was in 1974 when 58 people showed clinically significant disease. In recent years, there have been 1-2 clinically significant cases a year. The disease is under statutory reporting requirements in Australia.
The virus is not easily transmitted between individuals and is normally only transmitted by mosquito bites. The virus is normally carried by members of the genus Culex. The virus can survive in birds, especially waterfowl (herons, cormorants, and darters.), creating a reservoir that can cause continuing problems in the wake of an attack.
The dependence upon mosquito vectors suggests that an influx of mosquitoes would be indicative of an attack. Also, it suggests that effective protection against mosquito bites will blunt the attack.
Terrorist Acquisition and Attempted Use.
| Disease | ICD-9-CM | ICD-10 |
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| Murray Valley encephalitis |
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