¿Qué es el Sarampión?

Key Concepts

Measles, Morbilivirus, Contagious, Systemic Infection, Rash (Exanthema), Koplik's Spots, Croup, Pneumonia, Encephalitis, Immunosuppression, Vaccination, Herd Immunity, Anti-vaxxers, Maculae, Papulae, Cephalo-caudal Distribution, IgM, PCR, Viral Culture, Vitamin A Supplementation, Post-Exposition Prophylaxis, Immunoglobulin, MMR Vaccine, Anaphylaxis, Subacute Sclerosing Panencephalitis (SSPE).

Measles: An Overview

Measles is a highly contagious viral disease caused by the Morbilivirus. It spreads through the air and causes a systemic infection, typically characterized by a rash. While the rash is a classic symptom, immunocompromised individuals may not develop it. Measles can be lethal, especially in those with weakened immune systems or vitamin A deficiencies, leading to complications like croup (airway obstruction), pneumonia (the most frequent complication), and encephalitis (brain swelling).

Transmission and Pathogenesis

The virus enters the respiratory tract and proliferates. Infection requires contact with someone already infected. The virus is transported via the lymphatic system, leading to systemic infection and affecting various tissues, including the lungs. Measles causes immunosuppression, increasing the risk of secondary infections.

Mechanism of Infection:

1. Exposure (Day 0): Virus replication begins.
2. Contagious Period (Day 8): The patient becomes contagious, even without symptoms, as the virus is present in saliva and mucous.
3. Symptom Onset (Around Day 10): Fever (typically high, around 40ºC), body ache, lack of appetite, conjunctivitis, and cough develop.
4. Rash Appearance (Around Day 14): Maculae (red spots) and papulae (pimples) appear, starting on the head (cephalo-caudal distribution) and spreading downwards. Koplik's spots (white spots with red borders) appear in the oral mucosa near the second molars 1-2 days before the rash.
5. Resolution (Around Day 21): Symptoms subside, with cough being the last to disappear. The patient remains contagious for a few days after the rash disappears.

At-Risk Populations

• Individuals without two doses of the measles vaccine.
• Immunocompromised individuals (HIV, cancer, steroid use, malnutrition, vitamin A deficiency).
• Pregnant women (risk of complications and miscarriage).
• Children under 5 years old (high risk of complications).
• Adults over 20 years old (higher risk of complications).

Diagnosis

Diagnosis involves differentiating measles from other exanthematic diseases (chickenpox, herpes, acne, hives) based on the type of skin lesions (maculae, papulae, vesicles). Clinical evaluation has high sensitivity but low specificity. Confirmatory tests include:

• IgM Antibody Measurement: Antibodies against measles become positive around the 4th or 5th day of the disease.
• PCR Test and Viral Culture: The most specific tests, but not always available.

Complications

• Pneumonia: The main cause of death associated with measles.
• Croup: Acute airway obstruction.
• Keratitis: Infection of the cornea leading to blindness.
• Encephalitis: Brain inflammation.
• Superinfections: Due to immunosuppression.

Treatment

There are no specific antiviral drugs for measles. Treatment focuses on supportive care:

• Fever Management: Using NSAIDs (avoiding aspirin in children under 12).
• Vitamin A Supplementation: Especially in hospitalized children, to reduce morbidity and mortality.
  • Under 6 months: 50,000 units/day (2 doses)
  • 6-11 months: 100,000 units/day (2 doses)
  • 12+ months: 200,000 units/day (2 doses)
  • Vitamin A deficient patients may need a 3rd dose.
• Isolation: To prevent further spread.
• Contact Tracing: To identify and vaccinate exposed individuals.

Prevention

• Vaccination: Two doses of the MMR vaccine are needed for protection. The first dose is given at 12-16 months, and the second at 4-6 years.
• Herd Immunity: Achieved when at least 90% of the community is vaccinated.
• Post-Exposition Prophylaxis:
  • Vaccination within 72 hours of exposure can offer some protection.
  • Immunoglobulin administration (0.5 ml/kg for patients <30 kg, 400 mg/kg for patients >30 kg) can decrease the risk of complications.

Vaccine Effectiveness

Data from the United States shows a significant decrease in measles cases after the introduction of the vaccination program in 1964. The anti-vaxxer movement, fueled by fraudulent research, led to a drop in vaccination rates and a subsequent increase in measles cases.

Comparison of Measles vs. Vaccinated Patients:

| Complication | Measles Patients (per 100) | Vaccinated Patients (per 100) | | --------------------------------- | -------------------------- | ----------------------------- | | Otitis Media | 7 | 0 | | Diarrhea | 8 | 0 | | Pneumonia | 1-6 | 0 | | SSPE (per 100,000) | 4-11 | 0 | | Encephalitis (per 1,000) | 0.5-1 | <1 per 1,000,000 | | Death (per 1,000) | 1 (1-15% in poor healthcare) | 0 |

Known Vaccine Complications:

• Anaphylaxis: 2-14 per 1,000,000
• Decrease in Platelets: 1 in 30,000
• Fever-induced Convulsions: 1 in 3,000 (can be avoided with proper fever management)

Conclusion

Measles is a highly contagious and potentially dangerous disease, but it is preventable through vaccination. Maintaining high vaccination rates is crucial for achieving herd immunity and protecting vulnerable populations. While the vaccine has some known complications, the benefits far outweigh the risks. Education and awareness are essential for combating misinformation and promoting vaccination to eradicate measles.