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Emergency and Acute Medicine – Measles
Basics description
Measles, also known as rubeola, is a vaccine-preventable infectious disease that primarily affects children and is characterized by fever, cough, coryza, conjunctivitis, and an erythematous maculopapular rash. Due to widespread immunization, incidence is now low, but outbreaks continue to occur in nonimmunized or underimmunized populations.
Etiology
Measles is caused by the rubeola virus, a morbillivirus in the paramyxovirus family with negative-strand RNA. Humans are the only known reservoir. The virus is highly contagious and transmitted via respiratory droplets or direct contact; therefore, respiratory isolation must be initiated when measles is suspected. Outbreaks are most often associated with lapses in vaccination coverage.
Special populations
During pregnancy, measles infection increases the risk of spontaneous abortion and premature contractions but does not appear to cause congenital malformations. Pregnant patients should not receive MMR or MMRV vaccines. Adults born before 1957 are generally considered immune; however, health care workers should receive vaccination if serologic testing shows negative titers. In pediatrics, routine immunization with MMR or MMRV begins at ≥12 months of age, with a second dose at 4–6 years; catch-up doses must be spaced at least 4 weeks apart.
Diagnosis, signs, and symptoms
After an incubation period of approximately 10–12 days, patients develop a prodrome lasting 1–7 days with fever, malaise, cough, coryza, and conjunctivitis. Koplik spots—small white to grayish-blue lesions on the buccal mucosa—are pathognomonic and appear 1–2 days before the rash, disappearing shortly after rash onset. The classic maculopapular blanching rash develops 3–7 days into illness, beginning on the head and spreading downward. It may become confluent and occasionally petechial, rarely involving the palms and soles. Rash resolution occurs over several days and may be followed by desquamation.
Complications
Respiratory complications are common, with pneumonia occurring in approximately 6% of cases and representing the most frequent cause of death, particularly in immunocompromised patients. Otitis media, sinusitis, and diarrhea are also frequent. Neurologic complications include seizures and encephalitis, which may develop days after rash onset due to postinfectious autoimmune mechanisms. A rare but fatal late complication is subacute sclerosing panencephalitis, occurring years after infection. Cardiovascular complications such as myocarditis or conduction defects are uncommon but may be clinically significant in older adults.
Essential workup and diagnostic testing
Diagnosis is primarily clinical, based on the combination of fever, cough, coryza, conjunctivitis, and characteristic rash. Laboratory confirmation may include measles IgM and IgG serology or PCR for measles RNA. Viral isolation from blood, throat, nasopharynx, or urine is mainly for epidemiologic surveillance. CSF analysis is indicated if encephalitis is suspected, and chest radiography is obtained when pneumonia is a concern.
Differential diagnosis
Conditions to consider include rubella, scarlet fever, infectious mononucleosis, roseola, erythema infectiosum, enteroviral infections, Kawasaki disease, secondary syphilis, toxic shock syndrome, and drug reactions.
Treatment and emergency management
Management is primarily supportive, focusing on antipyretics, hydration, and monitoring for complications. Strict isolation is required. Postexposure prophylaxis for susceptible individuals includes MMR vaccination within 72 hours of exposure or intramuscular immune globulin within 6 days for high-risk contacts such as infants, pregnant patients, and immunocompromised individuals. Oxygenation and airway protection are essential in cases complicated by pneumonia or encephalitis.
Medications
The World Health Organization recommends vitamin A supplementation for children with measles, particularly in areas of deficiency, as it reduces morbidity and mortality. Dosing is age-based and administered once daily for two days.
Disposition and follow-up
Hospital admission is indicated for patients with severe pneumonia, dehydration, encephalitis, SSPE, immunocompromise, or significant comorbidities. Patients are contagious from 4 days before symptom onset until 4 days after rash appearance; immunocompromised individuals may remain contagious longer. Discharge is appropriate for stable patients without complications, with clear instructions on isolation and follow-up.
Pearls and pitfalls
Measles is one of the most contagious infectious diseases, with significant morbidity and mortality despite modern care. Early recognition and respiratory isolation are critical in health care settings. Immunocompromised patients may not develop the classic rash, increasing the risk of missed diagnosis. Vaccination remains the most effective preventive measure.
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