Measles Outbreak Associated With International Travel, Indiana, 2011

Background. Endemic measles was declared eliminated in the United States in 2000, but imported measles cases continue to cause outbreaks. On June 20, 2011, 5 epidemiologically linked measles cases were reported to the Indiana State Department of Health. We investigated to identify additional cases and to prevent further spread.Methods. Case findings and contact investigations during the June 3, 2011-August 13, 2011 outbreak identified measles cases, exposed persons, and exposure settings. Laboratory confirmation included measles serology and reverse-transcription polymerase chain reaction. Control measures included evaluating measles immune status and providing post-exposure prophylaxis, isolation, and quarantine.Results. Fourteen confirmed measles illnesses were identified (10 [71%] females; median age, 11.5 years [range, 15 months-27 years]). The source patient was an unvaccinated US resident who recently traveled from Indonesia. Twelve patients were unvaccinated members of the source patient's extended family. Two hospitalizations and no deaths were reported. Among 868 exposed persons identified through contact investigation, 644 (74%) had documented measles immunity, 153 (18%) were lost to follow-up, and 71 (8%) lacked evidence of immunity.Conclusions. Misdiagnosis of measles in an unvaccinated patient with recent travel history to a measlesendemic region resulted in the second largest measles outbreak in the United States during 2011. Clinicians should consider measles among patients presenting with febrile rash illness and history of recent travel, and clinicians should promptly report suspected illnesses. Early identification of infectious patients, rapid public health investigation, and maintenance of high vaccine coverage are critical for the prevention and control of measles outbreaks.