“…32 An ST-23 clone of serogroup Y accounted for much of serogroup Y disease at this time in both Canada and the USA. 33,34 During the 1990s in Canada, the incidence of both serogroup B and serogroup C disease fell (from ~0.4 per 100,000 population and 0.65 per 100,000 population respectively in 1993, to ~0.2 per 100,000 population and 0.1 per 100,000 population respectively in 1998) but remained the two most frequently observed causes of IMD. 21 By the end of the 1990s, serogroup C incidence had risen once again (to ~0.4 per 100,000 population in 2000; overall rate of disease was 0.78 per 100,000 in 2000), with the have been group W135, supporting an increase in prevalence of W135 disease during this period.…”