Measles (Rubeola)¶

Chapter 211 | Part 5: Infectious Diseases

KEY CLINICAL POINTS¶

Measles is a highly contagious viral disease caused by the Morbillivirus, characterized by fever, cough, coryza, conjunctivitis, and a generalized maculopapular rash.
Global measles incidence and mortality have decreased by 82% since 2000 due to vaccination, but outbreaks persist in low-coverage areas.
Measles vaccine (MMR) is safe and effective, with lifelong immunity following wild-type infection, though secondary immune responses may wane over time.
Complications include pneumonia, encephalitis, and SSPE, with case-fatality rates up to 20–30% in malnourished populations.
Passive immunization with measles immunoglobulin is recommended for high-risk contacts, while active immunization is contraindicated in severely immunocompromised individuals.

1. DEFINITION & OVERVIEW¶

Measles is a highly contagious viral disease characterized by a prodromal illness of fever, cough, coryza, and conjunctivitis followed by a generalized maculopapular rash. Before widespread vaccination, it caused >2 million deaths annually. Global measles incidence and mortality have decreased by 82% since 2000, but outbreaks persist in low-coverage areas. The World Health Organization (WHO) declared the Americas measles-free in 2016, though endemic transmission was reestablished.

Table 210-3 Recommendations for Poliovirus Vaccination of Adults¶

Recommendation	Details
General Population	Most adults in the U.S. have little risk; vaccination during childhood provides immunity
High-Risk Groups	Travelers to polio-endemic areas, lab workers, healthcare workers, and outbreak-associated populations
Unvaccinated Adults	Three doses of IPV at 4–8 week intervals; third dose 6–12 months after second
Previously Vaccinated Adults	Single lifetime booster dose of IPV recommended

1.1 Global Considerations¶

Measles vaccination has interrupted endemic transmission in the Americas, but outbreaks continue in regions with low coverage. No WHO region has sustained elimination status, emphasizing the need for high vaccination rates. The Measles and Rubella Partnership (MRP) works to improve immunization coverage globally.

2. EPIDEMIOLOGY¶

Measles is one of the most contagious pathogens, with outbreaks occurring in populations with <10% susceptible individuals. Incidence peaks in temperate climates during late winter/early spring due to social and environmental factors. Global measles deaths decreased from 772,854 (2000) to 136,216 (2022), but >100,000 children still die annually. The U.S. eliminated endemic transmission in 2000, but imported cases and low coverage threaten progress.

2.1 Risk Factors¶

Low vaccination coverage, immunocompromised states, malnutrition, and travel to endemic areas increase risk. Infants <6 months are protected by maternal antibodies, but those <9 months are susceptible if unvaccinated.

2.2 Demographics¶

Outbreaks occur in densely populated urban areas with low vaccination. Age distribution shifts to older children with higher coverage, but infants and young children remain at highest risk in low-coverage settings.

3. ETIOLOGY & PATHOPHYSIOLOGY¶

Measles virus is a nonsegmented, negative-sense RNA virus in the Paramyxoviridae family. It is transmitted via respiratory droplets and aerosols, with airborne transmission critical in enclosed settings. The virus replicates in respiratory epithelium, spreads via lymphatics, and causes systemic infection. Immune suppression occurs for weeks post-infection, increasing susceptibility to secondary infections.

3.1 Transmission¶

Respiratory droplets and aerosols (up to 8 hours in air). Airborne transmission is critical in schools, hospitals, and crowded environments. Direct contact with secretions is less common but possible.

3.2 Immune Response¶

Early innate responses (NK cells, antiviral proteins) and adaptive responses (IgM/IgG antibodies, T-cell responses) are critical. Immune suppression persists for weeks, increasing secondary infection risks.

4. CLINICAL FEATURES¶

The prodromal phase (fever, cough, coryza, conjunctivitis) lasts 4–5 days, followed by Koplik’s spots (pathognomonic) and a maculopapular rash. Complications include pneumonia, encephalitis, and SSPE. Severe cases in malnourished children may present with giant cell pneumonia.

4.1 Prodromal Phase¶

Fever, cough, coryza, conjunctivitis, and Koplik’s spots (bluish-white dots on buccal mucosa). Symptoms progress over 4 days.

4.2 Rash and Resolution¶

Rash begins 2 weeks post-infection, starting on face and spreading to trunk/limbs. Resolution may involve desquamation in malnourished children.

5. DIFFERENTIAL DIAGNOSIS¶

Rubella (milder, posterior auricular lymphadenopathy), roseola (rash after fever), infectious mononucleosis (atypical lymphocytosis), Kawasaki disease, and drug reactions. Differentiate based on rash morphology, fever pattern, and lymphadenopathy.

6. INVESTIGATIONS & DIAGNOSIS¶

Clinical diagnosis is reliable during outbreaks, but laboratory confirmation is required in low-prevalence areas. Serology (IgM/IgG) and RT-PCR for viral RNA are used. CDC case definition requires fever, rash, and respiratory symptoms.

6.1 Diagnostic Criteria¶

CDC case definition: generalized maculopapular rash ≥ 3 days, fever ≥ 38.3°C, and cough, coryza, or conjunctivitis. Serology (IgM) or PCR confirms acute infection.

7. MANAGEMENT & TREATMENT¶

Supportive care includes hydration, antipyretics, and antibiotics for secondary infections. Vitamin A (200,000 IU twice daily for ≥ 12 months) reduces mortality. Ribavirin has limited evidence of benefit. Immunoglobulin is recommended for high-risk contacts.

7.1 Supportive Care¶

Hydration, antipyretics, and antibiotics for bacterial complications. Vitamin A supplementation is critical for reducing morbidity/mortality.

7.2 Antiviral Therapy¶

Ribavirin may be used in immunocompromised patients, but evidence is inconclusive. No specific antiviral therapy is recommended for immunocompetent individuals.

8. PROGNOSIS & COMPLICATIONS¶

Case-fatality rate: 0.01–0.1% in developed countries, 5–10% in sub-Saharan Africa. Complications include pneumonia (most common), encephalitis, and SSPE. Immunosuppression increases risk of secondary infections and severe outcomes.

8.1 Severe Complications¶

Pneumonia (most common), encephalitis, and SSPE (progressive dementia). Giant cell pneumonia is common in immunocompromised patients.

8.2 Long-Term Effects¶

SSPE develops 5–15 years post-infection, with seizures and cognitive decline. Post-measles encephalitis occurs within 2 weeks of rash onset.

9. SPECIAL CONSIDERATIONS¶

Immunocompromised patients (e.g., HIV) are at higher risk for severe disease. Pregnant women should avoid live vaccines. Vitamin A supplementation is critical for infants and children. Passive immunization with immunoglobulin is recommended for high-risk contacts.

9.1 Pregnancy¶

Measles in pregnancy increases risk of miscarriage, prematurity, and congenital rubella syndrome. Vaccination should be avoided during pregnancy.

9.2 Immunocompromised Patients¶

Higher risk of severe disease, including giant cell pneumonia. Vaccination contraindicated in severely immunocompromised individuals.

10. KEY POINTS & CLINICAL PEARLS¶

Measles is a global public health priority; vaccination is the most effective prevention. Vitamin A supplementation reduces mortality. Immunosuppression after infection increases secondary infection risks. Passive immunization is critical for high-risk contacts. Global eradication requires sustained high vaccination coverage.