ESSENTIALS OF DIAGNOSIS
Exposure 7–18 days before onset of prodrome in an unvaccinated patient.
Prodrome: fever, coryza, cough, conjunctivitis, malaise, irritability, photophobia, Koplik spots.
Rash: brick red, maculopapular; appears 3–4 days after onset of prodrome; begins on the face and proceeds “downward and outward,” affecting the palms and soles last.
Measles is a reportable acute systemic paramyxoviral infection transmitted by direct contact with infectious droplets or by airborne spread. It is highly contagious with communicability greatest during the preeruptive and catarrhal stages but continues 4 days after the appearance of rash. Measles elimination is defined as the absence of endemic measles virus transmission in an area for 12 months or longer. Measles remains a major cause internationally of mortality with nearly 90,000 estimated deaths per year.
Between 2000 and 2016, the annual incidence of measles decreased by 87%, although in recent years the global tally of cases has increased, with the World Health Organization (WHO) estimating 7 million infections for 2016, the year with most recently compiled complete data. The WHO previously considered measles eradicated in the Americas. Major outbreaks, however, continue throughout the world (countries with over 1000 suspected cases in 2019 include Bangladesh, Cameroon, Chad, China, the Democratic Republic of the Congo, Georgia, Kazakhstan, Kyrgyzstan, India, Indonesia, Japan, Madagascar, Malaysia, Myanmar, Nigeria, the Philippines, Russian, Thailand, the Ukraine, and possibly Venezuela) and in the United States.
Most measles cases in the United States are due to either travel to endemic areas or exposure to individuals who have not been vaccinated against measles. A large 2015 outbreak at a California Disney theme park developed into a multistate outbreak involving 147 people. A 2017 outbreak in New York included 17 reported cases among unvaccinated Orthodox Jews and developed into a tristate outbreak. Additionally, 65 confirmed cases were identified in 2017 in a Somali-American community from Minnesota due to a decline in MMR vaccination coverage. The 2019 outbreak of measles includes 704 cases documented between January 1, 2019 and April 26, 2019 in 13 outbreaks occurring in 22 states with major outbreaks in California, New Jersey, New York, and Washington State. Previously, the highest number of reported measles cases was 667 in 27 states in 2014 followed by 372 in 2018. Intentional undervaccination continues to undermine measles elimination programs.
The incubation period for measles is 10–14 days. The illness starts with a prodromal phase manifested by high-grade fever (often as high as 40–40.6°C), malaise, coryza (nasal obstruction, sneezing, and sore throat resembling upper respiratory infections), persistent cough, and conjunctivitis (redness, swelling, photophobia, and discharge). These symptoms intensify over 2–4 days before onset of the rash and peak on the first day of the rash. The fever persists through the early rash (about 5–7 days) (...