What is the typical course of measles in children?

Typical Course of Measles in Children

Measles follows a predictable two-phase clinical course beginning with an incubation period of 10-12 days, followed by a prodromal phase with fever and the classic triad of cough, coryza, and conjunctivitis, culminating in a characteristic maculopapular rash that spreads from face to trunk over 2-4 days. 1

Incubation Period

• The incubation period averages 10-12 days from exposure to onset of prodromal symptoms and 14 days from exposure to rash appearance (range: 7-18 days) 1
• During this phase, the child is asymptomatic and not yet contagious 2

Prodromal Phase (Days 1-4 of Illness)

• High fever develops first, often reaching 103°F (39.4°C) or higher, accompanied by the pathognomonic triad of cough, coryza (runny nose), and conjunctivitis ("pink eye") 3, 1, 4
• Koplik spots appear during this phase—small white spots on a red background inside the mouth on the buccal mucosa—which are pathognomonic for measles and appear in approximately two-thirds of patients 3, 2, 4
• The child becomes highly contagious starting 4 days before the rash appears 3, 5

Exanthem Phase (Days 5-9 of Illness)

• After the prodromal symptoms, a second fever spike occurs along with the characteristic measles rash 2
• The rash is erythematous and maculopapular (or morbilliform), beginning on the face and spreading downward in a cephalocaudal progression to the trunk and then out to the extremities over 2-3 days 3, 1, 4
• The rash becomes more confluent as it spreads 4
• The child remains contagious through 4 days after the rash appears 3, 5

Common Complications

• Diarrhea is the most frequent complication, followed by otitis media (middle ear infection) and bronchopneumonia 1, 5
• Encephalitis occurs in approximately 1 per 1,000 cases, presenting with fever, altered mental status, and seizures, with potential for permanent brain damage 1, 6
• The case fatality rate in the United States is 1-2 per 1,000 reported cases 1

High-Risk Groups for Severe Disease

• Infants and young children under 12 months face the highest mortality risk 1, 7
• Immunocompromised children may develop severe, prolonged infection, sometimes without the typical rash, and may shed virus for several weeks after acute illness 3, 1
• Malnourished children, particularly those with vitamin A deficiency, experience higher complication rates and mortality 1, 2

Late Complication: SSPE

• Subacute sclerosing panencephalitis (SSPE) is a rare but invariably fatal late complication appearing years after initial infection, occurring in approximately 4-11 per 100,000 measles-infected individuals, particularly those infected at young ages 6

Critical Pitfall

The infectious period begins 4 days before the rash appears, meaning children are highly contagious during the prodromal phase when diagnosis may not yet be suspected—this explains why measles spreads so efficiently in unvaccinated populations 3, 5