685. An Outbreak of Measles in British Columbia, Canada: An Unwelcome Consequence of the 2010 Winter Olympics
Session: Abstracts: Virology
Friday, October 22, 2010
Background:  Fewer than 4 measles cases were reported annually in BC from 2002 to 2009. In 2010 a relatively large outbreak occurred. We describe the epidemiology of this outbreak and its implications for measles control.  

Methods: Standardized data collection and reconciliation with laboratory results were conducted.  Contact identification and post-exposure control measures were implemented.

Results: 85 cases were reported with onset dates from March 9 through April 28 peaking April 6th; all but 4 were laboratory-confirmed. Three measles virus genotypes were identified (H1 and two distinct D8 genotypes). The sources of infection were likely international visitors during the period of the Winter Olympic Games. Initial cases were in the Lower Mainland with spread throughout BC.

Sixty-one percent were born after 1980 (mean age 24 years). Thirty-five percent were unimmunized and 36% had unknown immunization history. Aboriginals make up 5% of the BC population but comprised 23% of cases, with 8 early cases linked to one large unimmunized household.  The proportion unimmunized was similar for aboriginal and non-aboriginal cases. A high proportion (60%) of cases sought emergency room medical care, 20% were hospitalized and one was admitted to intensive care.

Conclusion: This outbreak was the largest in BC since 1997, when 247 cases were reported. A measles elimination vaccine campaign was held in 1996 for children and adolescents in kindergarten through high school, and a routine 2-dose measles schedule was implemented the following year with the second dose given at 18 months of age. In the 2010 outbreak, unvaccinated and aboriginal people were overrepresented among cases, as would be anticipated for unimmunized persons, and due to active transmission out from an unimmunized large aboriginal household early in the outbreak. Measles 2-dose coverage in BC in 2009 was 73.7% at the 2nd birthday and 87.8% at kindergarten entry. Although an outbreak of this size is not inconsistent with a decade-long effective reproductive number below 1, sub-optimal vaccination rates contributed to transmission.


Subject Category: I. Adult and Pediatric Vaccines

Speakers:
Monika Naus, MD, MHSc , Epidemiology Services, British Columbia Centre for Disease Control, Vancouver, BC, Canada
Vanita Sahni, MHSc , Epidemiology Services, British Columbia Centre for Disease Control, Vancouver, BC, Canada
Reka Gustafson, MD , Vancouver Coastal Health, Vancouver, BC, Canada
Elizabeth Brodkin, MD , Fraser Health Authority, Surrey, BC, Canada
Rob Parker, MD , Interior Health Authority, Kelowna, BC, Canada
Murray Fyfe, MD , Vancouver Island Health Authority, Victoria, BC, Canada
William Osei, MD , Northern Health Authority, Prince George, BC, Canada
Mel Krajden, M.D., FRCPC , Public Health Microbiology and Reference Laboratory, British Columbia Centre for Disease Control, Vancouver, BC, Canada
Martin Petric, PhD, FCCM , Public Health Microbiology and Reference Laboratory, British Columbia Centre for Disease Control, Vancouver, BC, Canada
Graham Tipples, PhD , National Microbiology Laboratory, Winnipeg, MB, Canada
Measles Outbreak Group , Regional Health Authorities, British Columbia, BC, Canada

Disclosures:

M. Naus, None

V. Sahni, None

R. Gustafson, None

E. Brodkin, None

R. Parker, None

M. Fyfe, None

W. Osei, None

M. Krajden, None

M. Petric, None

G. Tipples, None

M. O. Group, None

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