How big is the Lyme problem? Using novel methods to estimate the true number of Lyme disease cases in British Columbia residents from 1997 to 2008.

Lyme disease (LD) is rare in British Columbia (BC) and, despite being a reportable condition since 1994, may be underreported. Here we review all provincial laboratory and clinical databases to determine the number of LD cases reported in BC from 1997 to 2008. We analyzed demographic characteristics of LD cases and used capture-recapture methodology to estimate the true number of cases in BC for this period. From 1997 to 2008, 93 confirmed cases of LD were reported in BC. Conservative capture-recapture estimates place the true number of LD cases in BC during this period at 142 (95% confidence interval: 111-224), indicating up to 40% underreporting of this rare disease. Despite this underreporting, BC continues to have low endemic risk of LD. Strategies are needed to increase both physician awareness and the use of preventive measures in the BC population, including for those traveling to other endemic areas.