In-depth Notes on Measles (Rubeola)

Measles Overview

  • Causative Agent: Measles virus (Rubeola)

  • Incubation Period: 10 to 12 days

  • Period of Communicability: From the fifth day of the incubation period through the first few days of the rash

  • Mode of Transmission: Direct or indirect contact with droplets

  • Immunity:

    • Natural Immunity: Contracting the disease provides lasting immunity.

    • Active Artificial Immunity: Attenuated live measles vaccine.

    • Passive Artificial Immunity: Immune serum globulin.

Terminology

  • Known as brown/black measles or 7-day measles which differentiates it from rubella (German measles or 3-day measles).

  • Due to high vaccination rates, measles is rarely seen except during outbreaks among under-immunized populations.

Disease Incidence

  • Highest Incidence: Winter and spring seasons.

Clinical Phases of Measles

  1. Prodromal Phase (10-11 days):

    • Lymphoid tissue enlargement, fever (103° to 104° F / 39.5° to 40.0° C), malaise.

    • Symptoms include:

      • Coryza (sore throat, nasal congestion with mucopurulent discharge)

      • Conjunctivitis with photophobia

      • Cough (deep brassy, bronchial cough)

    • Koplik’s spots: Bright-red spots with blue-white centers appear on the buccal membrane.

    • Common misdiagnosis as upper respiratory infection at this point due to overlap with cold symptoms.

  2. Rash Phase (around day 4 of fever):

    • Rash starts as a deep-red maculopapular eruption located initially at the hairline, behind ears, and neck, then spreads to the face, trunk, and extremities.

    • The rash progression typically follows a cranial to caudal pattern.

Transmission and Pathophysiology

  • The measles virus is transmitted via the respiratory system and replicates in the nasopharynx and regional lymph nodes 2 to 3 days post-exposure, leading to a secondary viremia.

  • Incubation to Prodrome: 10 to 12 days; Rash Onset: 14 to 21 days from exposure.

Variants and Conditions Related to Measles Virus

  • 22 known versions of the measles virus.

  • Six clinical forms of measles include:

    • Classic Measles: Typical presentation.

    • Modified Measles: Occurs in vaccinated individuals with inadequate immunity.

    • Atypical Measles: Results from prior vaccination with a killed virus vaccine (1963-1967).

    • Post-Infectious Neurologic Measles:

    • Causes conditions like ADEM and SSPE.

    • Severe Measles: Particularly harmful cases.

    • Complications: Giant cell pneumonia, measles inclusion-body encephalitis.

Clinical Symptoms
Phases of Classic Measles

  • Incubation: 8 to 10 days with no symptoms.

  • Prodrome: Lasts 2 to 8 days; symptoms are:

    • High fever (up to 105º F)

    • Dry cough

    • Coryza (runny nose)

    • Conjunctivitis

    • The Three "C's": Cough, Coryza, Conjunctivitis.

  • Koplik Spots: Red and white spots on the mucous membranes appear 1 to 2 days before the rash, serving as an important diagnostic indicator.

    • Appears approximately 48 hours before the generalized body rash.