Clinical Pearls & Morning Reports
All cases of suspected measles should be reported immediately — without waiting for diagnostic test results — to the local or state health department, which can assist with obtaining tests and take actions to minimize spread of virus. United States travelers to other countries account for a high proportion of imported cases of measles, which emphasizes the importance of measles vaccination of U.S. residents who are 6 months of age or older before international travel. Read the Clinical Practice article here.
Q: Describe some of the salient clinical features of measles.
A: Measles is an acute viral illness that starts with a prodromal phase, lasting 2 to 4 days, of fever and at least one of the “three Cs” (cough, coryza, and conjunctivitis), similar to any upper respiratory tract infection. The characteristic measles rash — an erythematous maculopapular exanthem — appears 2 to 4 days after the onset of fever, first on the face and head and then on the trunk and extremities; it may be confluent on the face and upper body. During the ensuing 3 to 5 days, the rash in different parts of the body fades in the order in which it appeared, and full recovery occurs within 7 days after rash onset in uncomplicated cases. Koplik spots, small bluish white plaques on the buccal mucosa, are present in up to 70% of cases and are considered pathognomonic of measles; they may appear 1 to 2 days before the onset of rash and may be present for an additional 1 to 2 days after rash onset.
Q: What complications may develop in patients with measles?
A: Complications associated with measles infection in industrialized countries include otitis media (7 to 9% of patients), pneumonia (1 to 6%), diarrhea (8%), postinfectious encephalitis (approximately 1 per 1000), subacute sclerosing panencephalitis (a progressive degenerative disease with onset usually 5 to 10 years after acute measles; approximately 1 per 10,000), and death (approximately 1 per 1000). The risk of complications is increased among infants, adults older than 20 years of age, pregnant women, undernourished children (particularly those with vitamin A deficiency), and persons with immune suppression (e.g., cancer or HIV infection).
A: Whereas a typical case of measles is easily recognized during outbreaks, the clinical diagnosis is challenging to many clinicians who have not seen measles and in patients who present before the onset of rash or whose rash is less apparent (e.g., infants with residual maternally acquired antibodies, previous receipt of immunoglobulin, or vaccination after exposure). The measles case definition recommended by the CDC (i.e., generalized maculopapular rash, fever [body temperature, ≥38.3°C], and cough, coryza, or conjunctivitis [or a combination of these symptoms]) has a high sensitivity (75 to 90%) but a low positive predictive value in low-incidence settings, indicating the need for laboratory confirmation. The most common laboratory method for confirming measles is detection of measles virus–specific IgM antibodies in a blood specimen (sensitivity, 83 to 89%; specificity, 95 to 99%). These antibodies are not detectable in approximately 25% of persons within the first 72 hours after rash onset but are almost always present after 4 days of rash.
A: Measles vaccine given within 72 hours after measles exposure, or human immune globulin given up to 6 days after exposure, can prevent or attenuate disease in susceptible persons. In household or classroom settings in which the timing of first exposure can be determined, prophylaxis has been shown to be highly effective (up to 90% after vaccine and 95% after immune globulin). Measles-containing vaccine should be considered for all exposed persons who do not have contraindications and who have not been vaccinated or have received only one dose of vaccine.