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Monday, August 11, 2025

Measles


Definition
Measles, also known as rubeola, is a highly contagious, acute viral illness caused by the measles virus, a single-stranded RNA virus belonging to the genus Morbillivirus within the family Paramyxoviridae. It is characterized by fever, cough, coryza, conjunctivitis, and a generalized maculopapular rash, often preceded by the appearance of Koplik spots inside the mouth.

Epidemiology

  • Measles remains a major cause of morbidity and mortality in unvaccinated populations, particularly in low- and middle-income countries.

  • Before widespread vaccination, measles affected nearly all children by age 15.

  • Although vaccine programs have reduced incidence significantly, outbreaks still occur due to declining vaccination rates and importation of cases.

  • Transmission occurs year-round but peaks in late winter and early spring in temperate climates.

Transmission

  • Spread by respiratory droplets and airborne transmission via coughing and sneezing.

  • Virus can remain infectious in the air or on surfaces for up to 2 hours.

  • Contagious period: From 4 days before rash onset to 4 days after rash onset.

Pathophysiology

Following inhalation, the virus infects respiratory epithelial cells and spreads to regional lymph nodes. A primary viremia disseminates the virus to the reticuloendothelial system, followed by a secondary viremia that spreads it to the skin, conjunctiva, respiratory tract, and other organs. The rash results from immune-mediated responses to infected endothelial cells in dermal capillaries.

Risk Factors

  • Lack of vaccination.

  • Immunodeficiency (HIV/AIDS, post-transplant, chemotherapy).

  • Malnutrition, particularly vitamin A deficiency.

  • Infants under 12 months who have not yet received the MMR vaccine.

Clinical Features

Incubation Period

  • Typically 10–14 days from exposure to onset of symptoms.

Prodromal Phase (lasts 2–4 days)

  • High fever (often >39°C).

  • Cough.

  • Coryza (runny nose).

  • Conjunctivitis (red, watery eyes).

  • Koplik spots: small bluish-white spots with red background on buccal mucosa opposite molars (pathognomonic).

Exanthem Phase

  • Maculopapular rash begins on the face/hairline, spreads to trunk and extremities over 3–4 days.

  • Rash becomes confluent, then fades in order of appearance, often leaving brownish discoloration and fine desquamation.

Other Symptoms

  • Sore throat, malaise, photophobia.

Complications

  • Respiratory: Pneumonia (most common cause of measles-related death).

  • Neurological: Acute disseminated encephalomyelitis (ADEM), measles inclusion body encephalitis, subacute sclerosing panencephalitis (SSPE).

  • Gastrointestinal: Diarrhea, dehydration.

  • Ocular: Keratitis, blindness (especially with vitamin A deficiency).

  • Otologic: Otitis media.

Diagnosis

Primarily clinical, supported by laboratory confirmation in outbreak or public health settings.

  • Serology: Detection of measles-specific IgM antibodies (positive within days of rash onset).

  • RT-PCR: Detection of viral RNA from throat/nasopharyngeal swabs or urine.

  • CBC: May show leukopenia, lymphopenia.

Management

General Principles

  • No specific antiviral cure; treatment is supportive.

  • Focus on symptom control, hydration, and prevention of complications.

1. Supportive Care

  • Adequate hydration and nutrition.

  • Antipyretics: Paracetamol (acetaminophen) 10–15 mg/kg every 4–6 hours (max 60 mg/kg/day in children; max 4 g/day in adults).

  • Tepid sponging for high fever.

  • Rest in a dimly lit room to reduce photophobia.

2. Vitamin A Supplementation

Recommended by WHO for all children with acute measles to reduce morbidity and mortality:

  • Children <6 months: 50,000 IU orally once daily for 2 days.

  • Children 6–11 months: 100,000 IU orally once daily for 2 days.

  • Children ≥12 months: 200,000 IU orally once daily for 2 days.

  • A third dose given 2–4 weeks later if signs of deficiency are present.

3. Antibiotics

  • Not for viral infection itself, but indicated for bacterial superinfection (e.g., pneumonia, otitis media).

  • Choices: Amoxicillin (child: 40–90 mg/kg/day orally in divided doses; adult: 500 mg orally every 8 hours).

4. Antiviral Therapy

  • No licensed antiviral for routine measles treatment.

  • Ribavirin (broad-spectrum antiviral) may be considered in severe immunocompromised cases:

    • Adult: 15–20 mg/kg/day IV in 3 divided doses; adjust per tolerance and renal function.

5. Post-Exposure Prophylaxis

  • MMR Vaccine: Administer within 72 hours of exposure for susceptible individuals.

  • Human normal immunoglobulin (HNIG): 0.5 mL/kg intramuscularly (max 15 mL) within 6 days for high-risk groups (infants <6 months, pregnant women without immunity, immunocompromised individuals).

Prevention

Vaccination

  • MMR (measles, mumps, rubella) vaccine:

    • First dose at 12–15 months.

    • Second dose at 4–6 years (or at least 4 weeks after the first).

    • Two doses provide ~97% protection.

Public Health Measures

  • Rapid case identification and isolation for 4 days after rash onset.

  • Contact tracing and post-exposure vaccination or immunoglobulin administration.

Prognosis

  • Most healthy, well-nourished individuals recover fully.

  • Higher morbidity and mortality in malnourished children, immunosuppressed individuals, and those with vitamin A deficiency.



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