measles

Measles (also known as rubeola) is a highly contagious infection caused by the measles virus.

Epidemiology

The measles vaccine, first introduced in 1963, has significantly reduced the incidences of measles. However, it remains endemic in countries with low vaccination rates . Worldwide, it is the leading cause of vaccine-preventable mortality in children .

Clinical presentation

Measles infection is divided into three distinct clinical stages:

  • incubation period:
    • the incubation period begins after the virus has infected an individual via the conjunctiva or respiratory mucosa
    • this stage ranges from 7-21 days
  • prodromal period:
    • the incubation period is followed by nonspecific prodromal symptoms of fevers, malaise, anorexia, cough, coryza and conjunctivitis
    • this phase usually lasts 2-4 days before the exanthem phase
    • Koplik spots are pathognomonic small blue-white spots on the buccal mucosa and appear 1-2 days before the onset of rash
  • exanthem:
    • after 2 to 4 days of prodromal period, the characteristic erythematous maculopapular rash appears
    • the rash is non-itchy and usually begins on the face and neck and progresses down to the entire trunk and extremities, rarely affecting the palms and soles
    • the rash begins to fade 3-7 days after first appearing, in the order of appearance

Pathology

Measles is highly contagious. The infection is transmitted from person-to-person via aerosolized respiratory droplets produced during coughing or sneezing. Approximately 90% of susceptible individuals develop measles after exposure to the virus. The measles virus can cause generalized immunosuppression and hence predisposes an individual, particularly those already immunocompromised, to secondary infection such as pneumonia .

Radiographic features

The role of imaging is to detect possible complications.

Plain radiograph

Chest radiography may demonstrate mixed reticular opacities, air space consolidation and lymph node enlargement in the hilum .

CT/MRI
  • the measles virus can affect the central nervous system and cause acute progressive encephalitis, acute post infectious encephalitis and subacute sclerosing panencephalitis
  • in acute encephalitis associated with measles, T2 weighted image shows widely distributed, multifocal high signal lesions in both cerebral hemispheres with swelling of the cortex and bilateral, symmetrical involvement of the dorsal striatum

Treatment and prognosis

There are no specific treatments for measles and the treatment is essentially supportive care with antipyretics, fluid therapy, and antibiotics for secondary bacterial infections.

Complications

Differential diagnosis