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Chapter 238 Measles

Measles is highly contagious and was once an inevitable experience during childhood. Owing to widespread vaccination, endemic transmission has been interrupted in the USA; indigenous or imported cases (in children or adults) have occasionally resulted in epidemics in the USA in unimmunized or partially immunized American or foreign-born children. In some areas of the world, measles remains a serious threat to children.


The measles vaccine has changed the epidemiology of measles dramatically. Once worldwide in distribution, endemic transmission of measles has been interrupted in many countries where there is widespread vaccine coverage. Historically, measles caused universal infection in childhood in the USA, with 90% of children acquiring the infection before 15 yr of age. Morbidity and mortality associated with measles decreased prior to the introduction of the vaccine as a result of improvements in health care and nutrition. However, the incidence declined dramatically following the introduction of the measles vaccine in 1963. The attack rate fell from 313 cases/100,000 population in 1956-1960 to 1.3 cases/100,000 in 1982-1988.

A nationwide indigenous measles outbreak occurred in 1989-1991, resulting in >55,000 cases, 11,000 hospitalizations, and 123 deaths, demonstrating that the infection had not yet been conquered. This resurgence was attributed to vaccine failure in a small number of school-aged children, low coverage of preschool-aged children, and more rapid waning of maternal antibodies in infants born to mothers who had never experienced wild-type measles infection. Implementation of the 2-dose vaccine policy and more intensive immunization strategies resulted in interruption of endemic transmission in the USA in 1993. The current rate is <1 case/1,000,000 population.

Measles continues to be imported into the USA from abroad; therefore, continued maintenance of >90% immunity through vaccination is necessary to prevent widespread outbreaks from occurring (Fig. 238-1).


Figure 238-1 Incidence* and percentage of import-associated measles cases, by year in the USA, 1985–2003.

(From the Centers for Disease Control and Prevention: Epidemiology of measles—United States, 2001–2003, MMWR Morb Mortal Wkly Rep 53:713–716, 2004.)

In 2008, 131 cases of measles were reported to the U.S. Centers for Disease Control and Prevention (CDC) in the first 7 months of the year, the highest year-to-date number of cases since 1996. Seven outbreaks accounted for 106 (81%) of the cases. Of the total, 17 patients (13%) had acquired the infection abroad and 99 cases (76%) were linked epidemiologically with the importations. These importation-associated cases occurred primarily among unvaccinated school-aged children whose parents had religious or philosophical objections to vaccination. Measles continues to be imported from abroad, and outbreaks will continue to occur in communities with low vaccination rates.

Clinical Manifestations

Measles is a serious infection characterized by high fever, an enanthem, cough, coryza, conjunctivitis, and a prominent exanthem. After an incubation period of 8-12 days, the prodromal phase begins with a mild fever followed by the onset of conjunctivitis with photophobia, coryza, a prominent cough, and increasing fever. Koplik spots represent the enanthem and are the pathognomonic sign of measles, appearing 1 to 4 days prior to the onset of the rash (Fig. 238-2). They first appear as discrete red lesions with bluish white spots in the center on the inner aspects of the cheeks at the level of the premolars. They may spread to involve the lips, hard palate, and gingiva. They also may occur in conjunctival folds and in the vaginal mucosa. Koplik spots have been reported in 50-70% of measles cases but probably occur in the great majority.


Figure 238-2 Koplik spots on the buccal mucosa during the 3rd day of rash.

(From Centers for Disease Control and Prevention: Public health image library, image #4500 [website].

Symptoms increase in intensity for 2-4 days until the 1st day of the rash. The rash begins on the forehead (around the hairline), behind the ears, and on the upper neck as a red maculopapular eruption. It then spreads downward to the torso and extremities, reaching the palms and soles in up to 50% of cases. The exanthem frequently becomes confluent on the face and upper trunk (Fig. 238-3).


Figure 238-3 A child with measles displaying the characteristic red blotchy pattern on his face and body.

(From Kremer JR, Muller CP: Measles in Europe—there is room for improvement, Lancet 373:356–358, 2009.)

With the onset of the rash, symptoms begin to subside. The rash fades over about 7 days in the same progression as it evolved, often leaving a fine desquamation of skin in its wake. Of the major symptoms of measles, the cough lasts the longest, often up to 10 days. In more severe cases, generalized lymphadenopathy may be present, with cervical and occipital lymph nodes especially prominent.