Measles is a highly contagious disease caused by the measles (rubeola) virus.

Epidemiology

• Prevalence - minimal number of cases yearly in U.S. due to the high rate of vaccination
  • >750,000 deaths worldwide
  • Occasional small outbreaks from imported cases of measles which affect primarily unvaccinated individuals
• Transmission
  • Via respiratory droplets
  •  Highly contagious; >90% transmission among non-immune individuals

Organism

• A single-stranded RNA virus and the only member of genus Morbillivirus (Paramyxoviridae family)
• Humans are the only natural reservoirs

Clinical Presentation

• Diagnosis based on clinical exam may be difficult, especially in atypical cases
• Highly contagious, acute, exanthematous respiratory disease with pathognomonic Koplik spots on the buccal mucosa
  • Cutaneous rash starts centrally and spreads to the periphery
• In atypical measles, rash begins peripherally and moves centrally
  • Atypical measles has occurred in patients who received killed vaccines and later came in contact with wild virus strain
• Severe, often fatal pneumonia can occur in patients with deficient cell-mediated immunity
• Complications
  • Pulmonary - primary giant cell pneumonia (Hecht pneumonia)
  • Neurological - coma, seizures, encephalitis
    • Subacute sclerosing panencephalitis (SSPE) - rare, progressive encephalitis that may result in dementia and death
    • Acute disseminated encephalomyelitis (ADEM)
    • Measles inclusion body encephalitis - immunocompromised patients
  • Gastrointestinal - disease mimicking appendicitis
  • Cardiovascular - myocarditis, pericarditis
  • Occular - corneal ulceration and scaring
  • Gestational - increased incidence of pneumonia in pregnant women, spontaneous abortion, premature delivery and low birth weight babies

Treatment

• Treatment of measles is largely symptomatic
• Vitamin A shown to be effective (American Academy of Pediatrics)
• Treat any secondary infections

Prevention

• Prevention includes MMR vaccine administered to 12-15 month old children, with revaccination between 4-12 years of age
  • High fever and pulmonary infiltrates can occur in patients vaccinated with Measles, Mumps and Rubella (MMR) 1964-67 and exposed to measles
    • Symptoms believed to be hypersensitivity reactions to the vaccine
  • Mass U.S. immunization has greatly reduced measles infections
    • However, some individuals may be susceptible to measles due to vaccine failure or non-immunization
• Since vaccine is live attenuated virus, do not use in pregnant patients or those with significant immunosuppression

Diagnosis 

• Indications for testing
  • Suspicious rash and clinical syndrome
  • Known exposure to measles in an unvaccinated person
  • Confirmation of immunity to measles after vaccination
• Laboratory testing
  • Serum testing for antibodies
    • Confirm acute infection with measles using IgM and IgG serial testing
    • Confirm seroconversion after vaccination using IgG testing
    • IgM, IgG CSF testing to identify SSPE (which may occur years after original infection using IgG testing)
  • Viral culture
    • Nasopharyngeal and blood cultures are most sensitive if collected during prodrome up to 1-2 days after onset of rash
    • Virus can be isolated from urine culture up to 1 week or more after onset of rash
    • Difficult to isolate from CSF and brain tissue
  • RT-PCR - not widely available, but useful for testing CSF

Differential Diagnosis

• Rubella
• Enterovirus
• Parvovirus B19
• Arboviruses
• Scarlet fever
• Kawasaki disease
• Dengue fever
• HIV
• Secondary syphilis
• Drug eruptions
• HHV-6/HHV-7