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Japanese 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) | Japanese encephalitis virus |
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| ICTV Acronym | JEV |
| 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 tritaeniorhynchus is the key vector in transmission to man and other species play a role in transmission among animal reservoirs. |
The first presentation is often as an aseptic meningitis.
Symptoms range from mild to fatal and almost invariably include a sudden onset of fever; anorexia and headache are common, while vomiting, nausea, diarrhoea and dizziness may also be experienced.
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 Japanese encephalitis is often subclinical and perhaps only 1 in 500 or more of those infected will go on to develop an encephalitis. For everyone else, the symptoms can range from mild to severe. The incubation period is 5-15 days and symptoms almost invariably include a sudden onset of fever; loss of appetite (anorexia) and headache are common. Vomiting, nausea, diarrhoea and dizziness may also be experienced.
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.
Severe cases may show hyperthermia (extremely high fever) accompanied by profuse sweating (diaphoresis), tachypnea (rapid shallow breathing) and accumulation of bronchial secretions.
When encephalitis develops, the mortality rate is about 25% and recovery almost always leaves some residual mental or functional disabilities including seizures, paralysis, ataxia and loss of mental and behavioral faculties.
Medical and Physical Countermeasures.
Vaccination (Immunoprophylaxis)
Vaccines are commercially available. 5-10% of people have some adverse reaction and the ill or pregnant women should postpone vaccination if possible.
Specific Therapy
none
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
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 and can survive in a number of mammals creating a reservoir that can cause continuing problems in the wake of an attack. Key reservoirs are pigs and large birds, especially herons.
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.
Even though development of full-blown encephalitis is uncommon, the neurological after-effects of large-scale infection will lead to significant numbers of victims needing prolonged support.
Japanese encephalitis is the commonest viral encephalitis of humans.
Terrorist Acquisition and Attempted Use.
| Disease | ICD-9-CM | ICD-10 |
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| Japanese encephalitis | 062.0 | A83.0 |
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