What are the recommended methods for testing and treating measles?

Testing and Treatment for Measles

Serologic testing with measles IgM antibody assay is the primary diagnostic method for measles, with specimen collection timing being critical for accurate results. 1

Diagnostic Testing for Measles

Clinical Case Definition

A clinical case of measles is characterized by:

• Generalized rash lasting ≥3 days
• Temperature ≥38.3°C (≥101°F)
• Cough, coryza, or conjunctivitis 1

Laboratory Testing Algorithm

1. First-line testing:

   • Collect blood for serologic testing during the first clinical encounter
   • Test for measles IgM antibody using a sensitive and specific assay (direct-capture IgM EIA method preferred) 1
   • Timing considerations:
     • IgM may be detectable at rash onset
     • Peaks approximately 10 days after rash onset
     • Usually undetectable 30-60 days after rash onset 1

2. If initial IgM test is negative:

   • For specimens collected within first 72 hours after rash onset
   • Obtain another specimen at least 72 hours after rash onset
   • Test again for measles IgM antibody 1

3. Alternative confirmatory methods:

   • Significant rise in measles antibody titer between acute and convalescent-phase serum specimens
     • Acute specimen: collected 1-3 days after rash onset
     • Convalescent specimen: collected 2-4 weeks later 1
   • Isolation of measles virus from a clinical specimen 1

4. Molecular characterization:

   • Collect specimen (urine or nasopharyngeal mucus) for virus isolation as close to rash onset as possible
   • Contact local/state health department immediately for specimen collection and shipping guidance
   • Note: This method requires considerable time and cannot be used for initial diagnosis 1, 2

Important Testing Considerations

• False positive results may occur with some commercial ELISA assays, particularly in patients with parvovirus infection
• Confirmatory testing with direct-capture IgM EIA method is recommended when:
  • IgM is detected in a patient with no identified source of infection
  • No epidemiologic linkage to another confirmed case exists 1
• Test for rubella in patients with febrile rash illness who are seronegative for measles 1

Treatment Approach

Measles treatment is primarily supportive as there is no specific antiviral therapy available 3:

1. Supportive care:

   • Manage fever and other symptoms
   • Ensure adequate hydration
   • Monitor for complications 3

2. Vitamin A supplementation:

   • Recommended for children to decrease mortality
   • Particularly important in younger children 3

3. Antibiotics:

   • Only indicated for bacterial superinfections
   • Not routinely prescribed unless complications develop 2

Public Health Response

1. Immediate notification:

   • Contact local/state health department immediately when measles is suspected
   • One confirmed case constitutes a public health emergency 1

2. Outbreak control measures:

   • Prompt vaccination of susceptible persons at risk for exposure
   • Do not delay control activities pending laboratory results
   • Exclude individuals without evidence of immunity from outbreak settings until 21 days after the last case 1

3. Post-exposure prophylaxis:

   • Vaccination can be effective when administered after exposure but before symptoms appear
   • Can prevent measles even when administered after a prolonged interval following exposure 4

Special Considerations for Infants

• If cases occur among infants <12 months, consider vaccination of infants as young as 6 months
• Children vaccinated before first birthday should be revaccinated at 12-15 months and again at 4-6 years 1, 5

Common Pitfalls to Avoid

• Delayed testing: Collect specimens as soon as measles is suspected
• Misinterpreting negative early results: IgM may not be detectable until 72 hours after rash onset
• Failure to notify public health authorities: Immediate reporting is essential for outbreak control
• Relying solely on clinical diagnosis: Laboratory confirmation should be attempted for all suspected cases
• Overlooking vaccination status: Verify immunity status of all contacts to prevent further transmission 1