Group A Strep Outbreak at Military Training Facility
Group A Streptococcus Outbreak in a Canadian Armed Forces Training Facility. Hammond-Collins K, Strauss B, Barnes K, Demczuk W*, Domingo MC, Lamontagne MC, Lu D, Martin I*, Tepper M. Mil Med. 2018 Aug 21. doi: https://doi.org/10.1093/milmed/usy198
This science story highlights the collaborative work and publication on an invasive Group A Streptococcus (iGAS) outbreak at a Canadian military facility. Findings from this work are being used to inform PHAC’s efforts to study and respond to this growing public health threat.
What was known about this area prior to your work, and why was the research done?
Group A Streptococcus (GAS) is usually a benign bacteria that can cause mild infections like strep throat or scarlet fever. However, given the right conditions, a GAS infection can become invasive (iGAS) and cause serious life threatening disease such as blood stream infections, toxic shock syndrome, and soft tissue infections such as flesh-eating disease (necrotizing fasciitis). In Canada, iGAS infections are on the rise, increasing 43% from 4.2 to 6.0 cases per 100 000 between 2010 and 2016. In this publication, we conducted an investigation into a 2017 iGAS outbreak at a Canadian Armed Forces (CAF) garrison in Quebec. This military base offers basic training and housing for recruits and personnel in a 13-story close quartered complex where GAS can be easily spread and transmitted. Prior to this outbreak, there were no reported iGAS outbreaks in the CAF. Very little is known about how GAS is disseminated through a population or why the seriousness of disease can vary from one person to another. Our investigation helped provide some insight into this. We identified a relatively rare GAS type (emm6.4) and explored how it spread though this controlled and confined population at the garrison.
What are your most significant findings from this work?
During the outbreak investigation, over 700 throat swabs were taken and 248 (35%) were positive for GAS, and 85 of these were all typed as emm6.4. Whole genome sequencing (WGS) was conducted on all emm6.4 isolates collected from the garrison, as well as some background emm6.4 isolates identified in other parts of the province. WGS data was used to determine strain relatedness as well as identify antimicrobial resistance determinants, toxins and virulence factors. The emm6.4 isolates collected from the military personnel were highly phylogenetically related and were distinct from the other circulating provincial background emm6.4 strains concluding that the garrison outbreak was due to local transmission among people within the garrison.
What are the implications or impact of the research?
Our investigation highlighted the need for a comprehensive surveillance system to monitor GAS and iGAS infections and for additional outbreak control practices. Our findings showed the high prevalence of GAS at this CAF garrison and the crowded communal spaces created the right environment for invasive cases to emerge and spread. As a result of our investigation, control measures were put in place at this garrison including: increased awareness of hygiene and respiratory etiquette, improved medical compliance, town hall briefings and modification of garrison culture (permission to break ranks to cough, limiting close yelling, and encouraging symptomatic recruits to seek medical care early). Further, our work changed policies including the development of clinical guidelines for standard practice and outbreak situations such as recommendations for mass prophylaxis for future GAS outbreaks at this CAF base. After a subsequent two-week rise in GAS cases was observed at this garrison in 2018, mass prophylaxis was administered resulting in the elimination of further GAS infections that season. Lessons learned from this outbreak investigation are currently being used to inform PHAC’s new iGAS treatment and outbreak guidance documents.
Additional References of Significance:
- Teatero S, McGeer A, J Tyrrell GJ, Hoang L, Smadi H, Domingo MC, Levett PN, Finkelstein M, Dewar K, Plevneshi A, Athey TBT, Gubbay JB, Mulvey MR, Martin I*, Demczuk W*, Fittipaldi N. Canada-Wide Epidemic of emm74 Group A Streptococcus Invasive Disease. Open Forum Infect Dis. 2018 Apr 20; 5(5):ofy085. doi: https://doi.org/10.1093/ofid/ofy085
- Sanchez JL, Cooper MJ, Myers CA, et al. Respiratory infections in the U.S. Military: recent experience and control. Clin Microbiol Rev. 2015 Jul; 28(3):743-800. doi: https://doi.org/10.1128/CMR.00039-14
- Hoe NP, Fullerton KE, Liu M, et al. Molecular genetic analysis of 675 Group A Streptococcus isolates collected in a carrier study at Lackland Air Force Base, San Antonio, Texas. J Infect Dis. 2003 Sep 15; 188(6):818-27. doi: https://doi.org/10.1086/377644
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