A community outbreak of travel-acquired measles, Ontario 2009

BACKGROUND: Canada has held elimination status for measles since 1998; however, imported cases continue to occur. OBJECTIVE: To describe the public health response to an imported measles case in the Waterloo Region of Ontario in May 2009. RESULTS: Contacts and exposures were traced, and cases were quickly investigated to identify the source. Through routine reporting mechanisms it was found that the index case had likely been exposed while on holiday in Disney World to a laboratory-confirmed measles case in a nine year old unimmunized boy from the United Kingdom (UK). Canada's National Microbiology Laboratory confirmed that the index case had the same D4 measles strain as the UK case and the strain that had been circulating in the UK. In total, one probable case and six confirmed cases were reported. The median age of confirmed cases was 14.5 years (mean age 17 years, range 6 to 39 years). Five confirmed cases (83%) were female. One confirmed case (17%) was hospitalized; no deaths were associated with the outbreak. CONCLUSION: This outbreak highlights the importance of collaboration with clinical care, the laboratory and public health at all levels of government to investigate and control a measles outbreak. Global travel and sustained local transmission may continue to pose a challenge with respect to the eradication of measles in developed countries.