Canada-Wide Epidemic of emm74 Group A Streptococcus Invasive Disease

Abstract

BackgroundThe number of invasive group A Streptococcus (iGAS) infections due to hitherto extremely rare type emm74 strains has increased in several Canadian provinces since late 2015. We hypothesized that the cases recorded in the different provinces are linked and caused by strains of an emm74 clone that recently emerged and expanded explosively.MethodsWe analyzed both active and passive surveillance data for iGAS infections and used whole-genome sequencing to investigate the phylogenetic relationships of the emm74 strains responsible for these invasive infections country-wide.ResultsGenome analysis showed that highly clonal emm74 strains, genetically different from emm74 organisms previously circulating in Canada, were responsible for a country-wide epidemic of >160 invasive disease cases. The emerging clone belonged to multilocus sequence typing ST120. The analysis also revealed dissemination patterns of emm74 subclonal lineages across Canadian provinces. Clinical data analysis indicated that the emm74 epidemic disproportionally affected middle-aged or older male individuals. Homelessness, alcohol abuse, and intravenous drug usage were significantly associated with invasive emm74 infections.ConclusionsIn a period of 20 months, an emm74 GAS clone emerged and rapidly spread across several Canadian provinces located more than 4500 km apart, causing invasive infections primarily among disadvantaged persons.

Increasing Rates of Invasive Group A Streptococcal Disease in Alberta, Canada; 2003–2017

“…Data from the Centers for Disease Control and Prevention’s Active Bacterial Core surveillance program (2010–2016) show that emm 74 was documented once from a case in Maryland in 2010 and that emm 101 has not been documented [ 20 ]. Although emm 74 increases were not evident in the United States in the years surveyed, increases in emm 74 have been reported in Ontario and other parts of Canada recently [ 28 ].…”

Out-of-season increase of puerperal fever with group A Streptococcus infection: a case–control study, Netherlands, July to August 2018

“…Invasive GAS infections such as streptococcal toxic shock syndrome (STSS), meningitis and fasciitis necroticans are rare but have a high morbidity and mortality. The incidence of invasive GAS infections is estimated to be 2.45 per 100,000 person-years in high-income countries, but seasonal variations and temporary increases of specific emm types have been described [ 3 , 5 - 7 ].…”

Risk for Invasive Streptococcal Infections among Adults Experiencing Homelessness, Anchorage, Alaska, USA, 2002–2015

“…Commonly identified risk factors for invasive GAS infection among adults include older age, male sex, exposure to children, household crowding, acute and chronic skin breakdown, immune-compromising conditions, heart disease, diabetes, and intravenous drug use ( 24 – 26 ), whereas established risk factors for invasive GBS among adults include immune-compromising conditions, heart disease, diabetes, and older age ( 27 , 28 ). Homelessness has not been previously quantified as a major factor for either type of infection, despite recent outbreaks of GAS among PEH ( 3 , 13 , 14 ). For invasive pneumococcus infection, risk factors include older age, immune-compromising conditions, alcohol use, high body mass index, and cigarette smoking ( 29 – 32 ).…”

“…During 2005–2009, an epidemic of invasive pneumococcal disease (serotype 5) was described in the homeless population in western Canada ( 11 ), and during 2009–2011, an outbreak of invasive pneumococcal disease (serotype 12F) among PEH was reported in Winnipeg, Manitoba, Canada ( 12 ). Starting in 2015, invasive GAS infections have emerged as a larger problem among PEH than previously recognized, as outbreaks began to be reported in the United States, Canada, and England ( 3 , 13 , 14 ).…”