Invasive Group A Streptococcal (iGAS) disease is a reportable disease to the Ministry of Health in the province of Alberta (pop in 2016; 4.25 million), Canada. This requires that all GAS isolates collected from cases of invasive disease in the province to be sent to the Provincial Laboratory for Public Health for emm typing. This process allows for identification of cases iGAS in Alberta.
From 2007 to 2016 (a 10 year period), the incidence rate of all iGAS ranged from a low of 4.8/100,000 in 2010 to a high of 7.6/100,000 in 2016. Rates of severe iGAS (necrotizing fasciitis and/or streptococcal toxic shock) ranged from a low of 0.8/100,000 in 2010 to a high of 1.63/100,000 in 2015.
Interestingly, the increase in rates has not been driven by any single emm type but rather by an overall increase in a collection of emm types. The top 5 emm types in 2007 by case numbers were: emm1 (36 cases), emm82 (30), emm59 (29), emm83 (22) and emm28 (18) and in 2016: the top 5 emm types were emm1 (60), emm101 (37), emm82 (28), emm59 (21) and emm83 (21). The increase in emm101 began in 2015 (26 cases) whereas in the previous 5 years, the number of cases averaged only 4.8/year.
In summary, incidence rates of iGAS disease have been increasing in Alberta, Canada over the last ten years. This increase has not been driven by any single emm type but rather a collection different emm types.