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Signs of Japanese Encephalitis Cardinal Signs of Japanese Encephalitis Clinical features of Japanese Encephalitis
Depending upon the disease process vis – a – vis involvement of Central Nervous System, the encephalitis can be categorised into 3 stages.

Prodromal Stage
Lasts 2–3 days. (Preceding the signs of CNS involvement).
Onset of the disease may be 1. Acute (less than 24 hours), 2. Sub acute (1–3 days), 3. Gradual (More than 3 days). The essential features of this stage are generalised malaise, headache and fever with chills & rigors in 90% of cases. The duration of this stage is between 1 – 6 days. It is observed that with rapid onset of disease, the case fatality will be higher. Hence, shifting the case to an appropriate medical care unit is vital at this stage.

Acute Encephalitis Stage
Lasts 3–4 days (is marked by CNS manifestastions).
The predominant features of this stage are continuous fever, neck rigidity, motor deficits, convulsions and altered sensorium progressing in many cases to coma. fever continues from prodromal stage, usually high and varies from 100.0 to 107.0 F. The patient sometimes presents with sudden behavioural changes like confusion, delirium, restlessness, disorientation, irrelevant speech, grasping etc. Speech disturbance like motor aphasia, dysphasia, monotonous speech may be observed. Abnormal spontaneous eye movement with absent corneal reflex and absent pupillary light reflex are also noted.

In acute stage, patient can exhibit signs of Raised Intracranial Pressure which can be identified by irregular breathing, headache, vomitting and asymmetric paralysis. Sometimes it may lead to convulsions & Coma.

Convalescent Stage (Recovery Stage)
Lasts 4–7 weeks. Marked by gradual recovery and sequaela.
After a period varying from few days to few weeks of acute stage, either steady improvement occurs or neurological deficits get established. This stage begins when active inflammation is subsiding, suggested by temperature and ESR coming to normal and neurological signs becoming stationary or tending to improve. Patients who recover from acute episode may have neurological sequelar with variable frequency. This depends on the age and severity of the illness.
Commonly observed sequelae are Movement disorders like Spasticity, Hemibalismus, Choreathetosis, Dystonic Myoclonus etc.

Physiotherapy and rehabilitation measures may be initiated in survivors with residual effects.