ESSENTIALS OF DIAGNOSIS
Onset of prodrome 7–18 days after exposure 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 of mortality with more than 140,000 estimated deaths globally in 2018, mostly in children younger than 5 years old.
As of April 2019, preliminary data from the World Health Organization (WHO) indicate that reported measles cases rose by 300% in the first 3 months of 2019, compared to the same period in 2018. The WHO previously considered measles eradicated in most countries worldwide, including the Americas. Many countries, however, are reporting ongoing measles outbreaks, including the Democratic Republic of the Congo, Nigeria, Guinea, Chad, Burundi, Madagascar, Central African Republic, Ethiopia, Philippines, Mexico, Yemen, Sudan, Ukraine, Brazil, Kazakhstan, Uzbekistan, India, and Bangladesh. During 2019, measles outbreaks occurred in countries with high vaccination coverage, including the United States, Israel, Thailand, Tunisia, New Zealand, and many European countries and the Pacific Islands. As of October 7, 2020, the WHO European Region reported a total of 12,028 measles cases. This is compared to 104,554 cases and 42 deaths in 2019.
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. Between January 1 and December 31, 2019, a total of 1282 measles cases and 22 measles outbreaks were reported in 31 states of the United States—the most cases reported in a single year since 1992. Included in this number are two large outbreaks in New York Orthodox Jewish communities, which accounted for 934 (75%) cases during 2019. 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, and many measles vaccination campaigns have been halted by COVID-19.
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 ...