Measles: Clinical Signs, Diagnostic Testing, and Treatment
Clinical Signs and Presentation
Measles should be suspected in any unvaccinated individual presenting with fever ≥38.3°C (≥101°F), a generalized rash lasting ≥3 days, and at least one of the "three Cs": cough, coryza (runny nose), or conjunctivitis. 1, 2
Key Clinical Features:
- Fever: Temperature ≥38.3°C (≥101°F) is required for clinical diagnosis 1, 2
- Rash characteristics: Erythematous maculopapular rash that begins on the face and spreads cephalocaudally (head to toe), becoming more confluent as it progresses 3, 4
- The "three Cs": At least one must be present - cough, coryza, or conjunctivitis 1, 2
- Koplik spots: Pathognomonic enanthem (small white spots on buccal mucosa) that may appear before the rash 3, 4
- Hyperpigmented rash: The maculopapular rash typically transitions to hyperpigmentation in approximately 89% of cases as the illness progresses 5
Important Timing:
The illness follows a characteristic pattern with a prodrome of high fever and the "three Cs" for 2-4 days, followed by the appearance of the rash 4
Diagnostic Testing
Serum measles-specific IgM antibody testing using the direct-capture IgM EIA method is the first-line diagnostic test and should be collected during the first clinical encounter with any suspected case. 1, 2
Testing Algorithm:
- Immediate collection: Obtain blood for IgM testing at the first clinical encounter, even if within 72 hours of rash onset 1, 2
- Timing considerations: IgM may not be detectable in the first 72 hours after rash onset with some assays 1, 2
- Optimal timing: Seropositivity rate is 92-100% when collected 6-14 days after symptom onset 1, 2
- Repeat testing: If the first IgM test is negative but collected within 72 hours of rash onset, obtain a second specimen ≥72 hours after rash onset 1, 2
Laboratory Confirmation Criteria:
A confirmed case requires one of the following 6, 2:
- Positive serologic test for measles IgM antibody
- Significant rise (four-fold or greater) in measles antibody level between acute and convalescent sera
- Isolation of measles virus from clinical specimen
- Detection of measles virus RNA by reverse transcriptase-PCR
Testing Pitfalls:
- False negatives: Can occur if specimen collected too early (within first 72 hours) 2
- False positives: May occur with parvovirus infection, other viral infections, or rheumatoid factor positivity 2
Other Laboratory Findings:
- Total WBC count is typically normal with lymphopenia and increased immature band forms 7
- Thrombocytopenia may occur (approximately 1 per 3,000 cases) 7
- Mild elevations in hepatic transaminases and hyponatremia may be present 7
Treatment and Management
Treatment is primarily supportive, with vitamin A supplementation recommended for all children with clinical measles. 1
Vitamin A Supplementation (WHO Recommendation):
Management of Complications:
- Bacterial superinfections: Treat with appropriate antibiotics 1, 3
- Diarrhea: Oral rehydration therapy 1
- Acute lower respiratory infections: Standard antibiotic treatment 1
- Supportive care: Monitor for complications including otitis media, laryngotracheobronchitis, pneumonia, stomatitis 8
Special Populations Requiring Aggressive Management:
Patients who are pregnant, immunocompromised, or unvaccinated may require additional interventions including measles vaccine (if appropriate timing), intravenous immunoglobulin, or ribavirin 9
No Specific Antiviral Therapy:
There is no specific antiviral therapy approved for measles treatment; disease control depends primarily on prevention and supportive care 8
Immediate Public Health Actions
Suspected and confirmed measles cases must be reported immediately to local or state health departments—do not delay reporting while awaiting laboratory results. 1, 2
Critical Infection Control Measures:
- Immediate isolation: Place patient in airborne infection isolation room with airborne precautions 9, 4
- Healthcare worker protection: N-95 masks required for all personnel entering the room 9
- Rapid investigation: One confirmed case constitutes an urgent public health situation requiring immediate investigation 1
- Contact tracing: Public health authorities will identify source of exposure and prevent further spread 6, 2
Case Classification for Reporting:
- Suspected case: Any febrile illness accompanied by rash 6, 1
- Probable case: Meets clinical case definition, not epidemiologically linked to confirmed case, and lacks laboratory confirmation 6, 1
- Confirmed case: Meets laboratory criteria OR meets clinical definition and is epidemiologically linked to confirmed case 6, 1