Measles is considered perhaps the most infectious disease known to humans, possibly equaled only by pertussis in its communicability.1,2 Measles was described and differentiated from smallpox by the Persian physician Al-Razi in the tenth century,3 but was not recognized as a viral disease until 1911, with the virus first successfully cultured in tissue in the late 1930s.4 In the prevaccine era, virtually every child became infected with measles. With increasing development and availability of vaccines in the 1960s, the incidence of disease decreased dramatically.5 Measles-containing vaccines were among the very first vaccines to be incorporated into the World Health Organization’s (WHO) Expanded Program on Immunization (EPI)—those recommended vaccines that every country should publicly promote and fund.6 The United States was able to achieve measles elimination (i.e., complete control of any endemic chain of transmission to < 12 months), in 1997.7 Today, all regions of the WHO have established target dates for measles elimination.8,9 However, recent years have seen striking increases in the number of measles cases, even in countries with historically robust immunization programs.10 Measles remains a sentinel disease whose emergence within a country may represent a failure of the government to provide timely vaccinations to all residents or an increase in vaccine hesitancy, a growing concern following the now-discredited study reporting a link between measles vaccination and autism.
Measles can be transmitted both through direct contact with large respiratory droplets and through indirect contact with measles virus in aerosolized droplet nuclei. Transmission of measles after the virus has been suspended in the air for over 2 hours has been documented.11,12 Infectiousness is extremely high, with 75–90% of susceptible household contacts developing disease.13
Measles has an incubation period of roughly 8–12 days before developing a characteristic viral prodrome initially consisting of high fever and malaise followed shortly thereafter by onset of cough, coryza, and conjunctivitis (the three Cs). Approximately 2–4 days after the viral prodrome, a distinctive erythematous, maculopapular rash appears consisting of lesions 3–8 mm in dimension, which spreads centrifugally starting on the face, before spreading to the trunk and extremities with the rash sometimes becoming confluent, especially on the face. Koplik’s spots, small blue-white enanthem in the mouth, are pathognomonic for measles, but are typically only seen 2 days before and after the onset of rash. Only about 62.5% of cases will develop Koplik’s spots.14 The patient’s temperature peaks 1–3 days following rash with fever as high as 104 degrees, with gradual fading of the rash about 3–7 days after onset in order of its appearance on the patient’s body. Measles typically resolves 10–14 days after symptom onset.13
Complications and death are not uncommon after measles infection. In the United States, prevalent complications include diarrhea (8%), otitis media (7%), and pneumonia (6%).13,15 The rate of complications, including morbidity and mortality, ...