What are the clinical presentation, diagnostic work‑up, management, and prevention strategies for measles in an unvaccinated child or adolescent?

Measles in Unvaccinated Children and Adolescents

Clinical Presentation

Measles presents as an acute febrile illness with a characteristic progression: fever combined with cough, coryza, or conjunctivitis, followed 3-4 days later by a maculopapular rash that begins on the face and spreads cephalocaudally. 1

Prodromal Phase

• Fever is the initial manifestation, accompanied by at least one of the "3 Cs": cough, coryza (runny nose), or conjunctivitis 2, 3
• Koplik spots (pathognomonic enanthem on buccal mucosa) may appear before the rash, providing diagnostic opportunity 2, 3
• This prodromal phase typically lasts 2-4 days 1

Exanthematous Phase

• Erythematous, maculopapular rash appears 3-4 days after fever onset 2, 3
• Rash initially appears on the face and behind the ears, then spreads downward (cephalocaudal progression) 3
• Rash becomes more confluent as it spreads, with peak symptoms coinciding with rash appearance 2

Critical Caveat

• Vaccinated individuals can present with milder or even no symptoms, making diagnosis more challenging 1

Diagnostic Work-Up

Laboratory confirmation should be obtained immediately when measles is suspected, but control measures must not be delayed pending results. 4

Immediate Actions

• Contact local or state health department immediately upon suspecting measles—one confirmed case constitutes an urgent public health situation 4
• Prompt investigation of all suspected cases is mandatory due to rapid disease spread potential 4

Laboratory Confirmation Methods

• Measles-specific IgM antibody detection in serum, dried blood spots, or oral fluid (primary diagnostic method) 1, 3
• Four-fold or greater increase in measles-specific IgG between acute and convalescent sera 3
• Viral RNA detection by reverse transcriptase-PCR in throat/nasopharyngeal swabs, urine, or oral fluid 1, 3
• Viral culture isolation (time-consuming, not practical for acute diagnosis) 4

Important Diagnostic Consideration

• If measles-like illness occurs shortly after vaccination in exposed persons, specimens should be submitted for viral strain identification to distinguish natural infection from vaccine strain 4

Management

Treatment is primarily supportive with no specific antiviral therapy available; focus on preventing complications and treating secondary infections. 1, 5

Supportive Care

• Vitamin A supplementation is recommended for all children with clinical measles to reduce mortality risk 6, 1, 5
• Correction of dehydration with oral rehydration therapy, especially for severe diarrhea 6, 1
• Nutritional support to address deficiencies 2
• Monitoring for complications affecting multiple organ systems 1

Treatment of Complications

• Prompt antibiotic therapy for secondary bacterial infections (otitis media, pneumonia) 6, 1, 5
• Pneumonia is the most common cause of measles-related death and requires aggressive management 6, 7

High-Risk Populations Requiring Intensive Monitoring

• Infants and young children under 3 years face greatest mortality risk 6, 7
• Immunocompromised individuals (leukemia, lymphoma, HIV) experience severe, prolonged infection with atypical presentations 8, 7
• Pregnant women have increased risk of premature labor, spontaneous abortion, and maternal/fetal mortality 6, 7
• Malnourished children have significantly elevated mortality risk 6, 7

Serious Complications to Monitor

• Acute encephalitis occurs in approximately 1 per 1,000 cases (0.1%) and is a leading cause of death 6, 7
• Subacute sclerosing panencephalitis (SSPE) is a rare but uniformly fatal late complication appearing 6-8 years post-infection 8
• Immune suppression persists for weeks to months after infection 5

Prevention Strategies

All unvaccinated children and adolescents should receive two doses of MMR vaccine: first dose at 12-15 months and second dose at 4-6 years, with catch-up vaccination for those who missed scheduled doses. 8, 5

Routine Vaccination Schedule

• First MMR dose at 12-15 months of age 4, 8
• Second MMR dose at 4-6 years (before school entry) 4, 8
• The second dose addresses the approximately 5% primary vaccine failure rate from the first dose 8

Catch-Up Vaccination

• Adolescents and adults born after 1957 without documentation of two MMR doses or laboratory evidence of immunity should receive catch-up vaccination 8
• Unvaccinated persons who cannot provide acceptable evidence of measles immunity should be vaccinated immediately 4

Outbreak Control Measures

• Immediate vaccination of susceptible persons at risk for exposure helps prevent dissemination 4
• Persons lacking acceptable immunity should be vaccinated or excluded from outbreak settings (schools, day care, hospitals) for 21 days after rash onset in last case 4
• Revaccination with MMR is recommended for all attendees in affected day care facilities and schools who have not received two doses 4

Post-Exposure Prophylaxis

• MMR vaccine within 72 hours of exposure can provide protection 4
• Immune globulin (IG) may be preferred for infants <12 months who are household contacts, especially if exposed >72 hours before diagnosis 4
• MMR vaccination will not exacerbate symptoms if person is already incubating measles 4

Special Outbreak Situations

• Infants 6-12 months may receive early MMR vaccination during outbreaks (monovalent measles vaccine preferred), but must be revaccinated at 12-15 months and again before school entry 4
• Early vaccination before 8.5 months should only be considered during outbreaks or high-risk situations, as it leads to markedly faster antibody decay and blunted responses to subsequent vaccination 9

Critical Prevention Point

Vaccination is the only effective strategy to prevent SSPE and has essentially eliminated this uniformly fatal complication in highly vaccinated populations. 8 Measles elimination requires 93-95% population coverage with two vaccine doses 5