Measles

• Paramyxoviridae

• Morbillivirus,
• ssRNA, -ve sense
• Pleomorphic
• 120-250nm
• enveloped
• natural reservoir in humans

• Child

• 5-9 in UK
• <2 in developing countries

Clinical Features

• Incubation 7-14 days, usually 10
• Prodrome 2- 4 days
  • Fever, coryza, unproductive cough, conjunctivitis
• Rash
• Pathognomic of measles
• Occurs at end of prodromal period
• Starts with Koplik spots
  • Blue/grey on red base
• Erythematous
• Maculopapular
• Typical course
  • Day 1 – starts behind ears
  • Spreads to face
  • Day 2 – spreads downwards
  • Day 3 confluent on face and neck
  • Last about 5 days
  • Leaves brownish pigmentation but no scarring

• Infectious period from prodrome until 4 days after rash develops

Pathogenesis

• Respiratory tract epithelium, endothelial cells, monocyte macrophages
• Regional lymph nodes
• Thymus, spleen, appendix, tonsils, skin, conjunctivae, liver, lung, GU, GI
• LAP, SM, appendicitis

Complications

• Respiratory
  • Interstitial pneumonitis
    • Generally asymptomatic except in pregnancy
  • Secondary viral or bacterial pneumonia
  • Giant cell pneumonia
  • Otitis media – 2.5%
  • Laryngotracheobronchitis in under 2s
• Central Nervous system
  • Post-infectious encephalitis
    • 1:1000
    • Normal host <2
    • Recrudescence of fever, headache, seizures, cerebellar ataxia, multifocal signs, declining level consciousness
    • Pathology – inflammation, demyelination, no MV (?)
    • Monophasic over weeks
    • Poor prognosis – 15% mortality, 40% sequelae
  • Subacute sclerosing encephalitis
    • 1:10⁶
    • Normal host <2yr
    • Intellectual deterioration, motor dysfunction, dyspraxia
    • Pathology
      • Inclusion bodies
      • Inflammation
      • Measles virus
    • High antibody titres against measles virus in CSF
    • Progressive, death in 1-3 years
  • Measles Inclusion Body Encephalitis
    • Rapidly progressive
    • Increased incidence in the immunocompromised
    • Occurs 1-6 months after exposure
    • Usually causes retinopathy
• GI tract
• Cardiovascular
• Eye

Epidemiology

• Risks of morbidity and mortality
  • Age <1 or >9 years old
  • Underlying illness
  • Defects of cellular immunity
  • Malnutrition
  • Poverty
• Up to 1 million deaths /year
• 5-15% mortality in developing countries

Variants

• Atypical measles
  • After formalin killed measles vaccine (1963-8)
  • Exposure to live measles altered CMI responses
• Modified – milder form (lower immunity)

Differential

• Rubella, parvovirus B19
• Exanthem subitum / 6^th disease
• Drug reaction
  • Don’t show typical head downwards pattern of rash
• Secondary stage syphilis
• Early meningococcal septicaemia
• Erythema multiforme

Diagnosis

• Throat swab
• Serum (1-2) days
  • Antibody responses – IgM and IgG
  • 4 fold rise in IgG, single IgM
  • RT-PCR
• Nasopharyngeal aspirate (1-2days)
  • Detection of multinucleate giant cells with inclusion bodies in nasopharyngeal secretions
  • Immunofluorescence of cells in nasopharyngeal secretions
• Urine
  • Immunofluorescence of cells (>1 week)
• CSF
  • Virus isolation (rare)
• Tissues specimens
• Saliva
  • Special swabs available

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