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Measles outbreak linked to unvaccinated international travel
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The 2011 Indiana measles outbreak, the second largest in the United States during 2011, was found to result from the misdiagnosis of an unvaccinated US resident who had recently returned from international travel to a measles-endemic region.
Although endemic measles was declared eliminated in the US in 2000, imported measles cases have continued to cause outbreaks, according to researchers.
“The public underestimates vaccine preventable disease as a cause of morbidity and mortality when incidence of disease is low for a prolonged period, and common reasons for parents not vaccinating their children are fears of adverse events and the perception that their children are safe because of high vaccination rates in the community,” Melissa G. Collier, MD, MPH, a medical epidemiologist with the LCDR United States Public Health Service, and colleagues wrote.
On June 20, 2011, five epidemiologically linked measles cases were reported to a local health officer in rural Indiana by an emergency physician. To identify measles cases, exposed persons and exposure settings, Collier and colleagues launched a public health investigation to examine case findings and contact investigations during the outbreak.
Laboratory confirmation of the illness included measles serology and reverse-transcription PCR, and the researchers enacted various control measures, including evaluating measles immune status and providing post-exposure prophylaxis, isolation and quarantine.
According to results of the investigation, among 38 suspected cases investigated for measles, 14 confirmed cases were identified (10 [71%] females; median age, 11.5 years [range, 15 months-27 years]).
The source patient, a US resident aged 24 years, unvaccinated for philosophic reasons, returned to the US after living in Indonesia for a year — 12 patients were unvaccinated members of the source patient’s extended family.
The source patient had experienced chills and a generalized maculopapular rash during the return flight, but temperature was not measured and no additional prodromal symptoms were reported. She was later admitted to a hospital and treated for dehydration and presumed dengue fever rather than measles and she was not isolated.
“The attack rate among unvaccinated family members was 92%, highlighting the measles infectiousness,” Collier and colleagues wrote. “Transmission among family members could have been prevented if the diagnosis was made earlier. Two patients were ill enough to require hospitalization for a total of 5 days.”
Among 868 exposed individuals identified through contact examination, the researchers observed that 644 (74%) exhibited documented measles immunity, 153 (18%) were lost to follow-up and 71 (8%) lacked evidence of immunity.
“Parents should be educated on the importance of vaccinations for children, despite high vaccination rates in their communities, to prevent measles among high-risk groups, such as pregnant women, immunocompromised persons, and children too young to be vaccinated,” Collier and colleagues wrote. “Physicians should inquire about recent travel and immunization status when evaluating patients with measles-like symptoms and report suspected cases to public health officials.”
Disclosure: The researchers reported no relevant financial disclosures.