Measles Incubation Period: Timeline & Contagiousness

Incubation period: 7–18 days (average 10–12) from exposure to symptom onset.

Disease Timeline

• Days 0–7: Exposure → viral replication in respiratory mucosa → lymph nodes.
• Days 7–18: Viremia → systemic spread.
• Prodrome (2–4 days): Fever (up to 40°C), cough, coryza, conjunctivitis ("3 Cs"), Koplik spots (pathognomonic, buccal mucosa).
• Exanthem (rash): Day 3–5 of illness. Maculopapular, starts face/hairline → spreads downward. Confluent. Fades in same order.
• Contagious: 4 days before rash → 4 days after rash onset. Peak: prodrome.

Key Points

• R₀ = 12–18 (highly contagious; airborne).
• Vaccine: MMR (live attenuated) 97% effective after 2 doses.
• No specific antiviral; supportive care. Vitamin A reduces mortality in deficient populations.
• Complications: pneumonia, encephalitis (1/1000), SSPE (rare, fatal, years later).

Isolate immediately if suspected. Notify public health.