Measles Outbreak in DuPage County, IL

Seven school-age children have contracted measles (rubeola) in DuPage County, IL, approximately 30 miles west of Chicago, according to the Illinois Department of Public Health. Investigation is pending, and the source of the infection remains unknown; however, inadequate immunization appears to be the cause of the outbreak.

In early May, the MMWR reported 64 cases of measles from January 1 to April 25 in the United States. A case of measles imported from Switzerland occurred April 17 in Chicago. As of May 23, the CDC has confirmed 103 US cases this year, the highest number for this time period since 2001.

Measles is spread by respiratory droplets or fomites, and infection occurs in 90% of those who are not vaccinated. The incubation period of the virus is 10-12 days, which is followed by mild-moderate fever, persistent cough, rhinitis, conjunctivitis, and pharyngitis. Approximately 3 days later, high fever, Koplik's spots (view image), and the characteristic skin rash (view image) appear. The measles rash—typically erythematous, blotchy, and slightly pruritic—begins on the face, hairline, and behind the ears and progresses to the chest, back, thighs, and feet. After approximately 2 weeks, the rash fades in reverse order.

Complications of measles include otitis (1/10), pneumonia, (1/15), encephalitis (1/1000), and thrombocytopenia. Pregnant women should avoid exposure to measles, owing to associated risks of miscarriage, premature labor, and low-birth-weight infants.

Measles cases are highly contagious, beginning 4 days before the rash appears and lasting until 4 days after the rash disappears. Vaccination confers approximately 98% immunity. The CDC recommends that all children should receive 2 doses of MMR vaccine (at 12-15 months and at 4-6 years). Adults without documented immunity should receive at least 1 MMR dose. International travelers should undergo age-dependent vaccination. Illinois reports an immunization coverage level among school-age children of 98%; however, the state does offer personal and religious exemptions.

Map of DuPage County from Wikipedia Commons.

Photos of Koplik's spots and measles rash from CDC.