The reasoning: JE epidemiology
| Feature | Detail |
|---|---|
| Agent | JE virus (flavivirus) |
| Cycle | Ardeid water birds (herons, egrets: reservoir) ↔ **Culex tritaeniorhynchus, C. vishnui (rice fields) ↔ pigs (amplifying hosts: high viraemia, abortion and stillbirth in sows) → humans and horses (dead‑end hosts**) |
| Ratio | ≈ 1 symptomatic case per 250–1,000 infections |
| Age | Children < 15 years in endemic areas; adults in newly affected areas (adult vaccination in high‑burden districts) |
| Clinical | Fever, headache, vomiting → altered sensorium, seizures, extrapyramidal features; CFR 20–30%; ≈ 30–50% of survivors have neuro‑psychiatric sequelae |
| Season | Monsoon and post‑monsoon (paddy cultivation) |
| Distribution | UP, Bihar, Assam, West Bengal, Tamil Nadu, Karnataka, Andhra Pradesh and others |