Lecture Notes: Measles

Introduction

• Highly contagious infectious disease.
• Leading cause of death, especially among young children in areas with low vaccination rates.
• Also known as rubeola, not to be confused with German measles (rubella).

Virology

• Caused by the measles virus, genus Morbillivirus, family Paramyxoviridae.
• Airborne transmission via tiny liquid particles from sneezes or coughs.
• Virus can live up to 2 hours in the air or on surfaces.
• Extremely contagious: 90% infection rate among non-immune close contacts.

Pathogenesis

• Infects epithelial cells in trachea or bronchi using hemagglutinin (H protein) and other receptors like CD46, CD150 (SLAM), and Nectin-4.
• Single-stranded RNA virus, negative sense; transcribed by RNA polymerase into mRNA.
• Spreads to lymph nodes, blood, and other organs like lungs, intestines, and brain.

Clinical Course

1. Incubation Period: 10-14 days from exposure to symptom onset.
2. Prodromal Period: Lasts around 3 days; includes high fever, cough, conjunctivitis, choriza.
   • Appearance of Koplik's spots (enanthem) inside cheeks.
3. Exanthem Phase: Red, blotchy rash spreads from head to extremities; rash fades after about 4 days.
4. Recovery Phase: Lasts another 10-14 days; final symptom often a persistent cough.

• Contagious from 4 days before to 4 days after rash onset.
• Lifelong immunity post-recovery.

Complications

• Pneumonia, diarrhea, encephalitis.
• Immune suppression for up to 6 weeks leading to bacterial infections like otitis media.
• Higher mortality in young infants.
• Risk of subacute sclerosing panencephalitis (SSPE) 7-10 years post-infection.
• Immunocompromised individuals may have atypical symptom presentation but higher complication rates.

Diagnosis and Prevention

• Diagnosed via serology: measles antibodies in blood serum.
• Disease most common in unvaccinated individuals.
• Vaccine Information:
  • Live attenuated vaccine given at 12-15 months and 4-6 years.
  • 95% efficacy rate.
  • Maternal antibodies provide protection up to 9 months.

Treatment

• No specific antiviral treatment.
• Focus on treating superinfections, maintaining hydration, and pain relief.
• Vitamin A prescribed to some groups to boost immune response.

Outbreak Management

• Vaccination for household contacts.
• Measles immunoglobulin for pregnant women and young infants.

Summary

• Measles is a highly contagious airborne pathogen.
• Causes cough, conjunctivitis, choriza, and complications like pneumonia, encephalitis.
• Preventable through vaccination.