The Health Protection Surveillance Centre (HPSC) has detected an increase in notifications of invasive Group A Streptococcal (iGAS) infections in Ireland during quarter 1 2016. Between January and March 2016, there were 49 iGAS notifications reported to the Computerised Infectious Disease Reporting (CIDR) system compared with 20 for the same period in 2015, representing an almost 2.5-fold increase. There were 53 iGAS notifications in the first quarter of 2014.

In March 2016, there were 26 notifications, which is the joint highest monthly figure reported to date. The increasing trend in early 2016 can be seen in Figure 1, which shows the numbers of iGAS cases by month and year. As iGAS disease demonstrates a seasonal distribution with the peak months for notifications occurring between spring and summer months, this upsurge may continue through 2016. The increase observed could possibly be associated with the influenza season this past winter, which was described as moderate-to-severe (based on the data up to 10^th April 2016).

Figure 1.Monthly data of iGAS cases notified by year, January 2008-March 2016 

Analysis of the data by HSE Area indicates that the biggest increases in iGAS cases during Q1 2016 occurred in the east of the country with the HSE East reporting 28 cases, compared to 9 in Q1 2015, and the HSE North-East reporting 5 cases, compared to none in Q1 2015 (Figure 2).

Figure 2. Distribution of iGAS cases by HSE Area, Q1 2016 compared to Q1 2015
HSE Areas: E, East; M, Midlands; MW, Mid-West; NE, North-East; NW, North-West; SE, South-East; S, South; W, West

The national iGAS Typing Service examined 35 isolates of the 49 cases reported in Q1 2016 (data as of 8^th April 2016) and found that 14 (of the 35; or 40%) belonged to emm1 representing an increase on Q1 2015 when 5 (of 20 isolates typed; or 25%) were emm1. The numbers of other emm-types are too small as yet to determine if any other changes in the predominating emm-types are occurring.

Periodic upsurges in iGAS infections have been reported previously in Ireland and other countries. These upsurges are not fully understood, but it is thought that changes in circulating strains, population susceptibility and the prevalence of risk factors among vulnerable populations may play important roles. A similar increase in iGAS disease has been reported recently in some parts of England by Public Health England. A prolonged upsurge in iGAS disease in Ireland was observed between May 2012 and Sept 2014. This was associated with an increase in the number of cases presenting with streptococcal toxic shock syndrome (STSS) and a higher mortality rate among STSS cases. emm-typing revealed that two emm-types, emm1 and emm3, were associated with the increase over this period with emm1 predominating in 2012, both emm1 and emm3 in 2013 and emm3 in 2014. Some emm-types, such as emm1 and emm3, are known to be associated with more severe disease and increased mortality. Other risk factors including infections with certain viruses (e.g. influenza and varicella) may also predispose to iGAS infection.

Clinicians should be made aware of the recent increase in iGAS and reminded of the possible early signs and symptoms of iGAS disease.

Microbiology laboratories are kindly requested to send any iGAS isolates for emm-typing to: Dr Mary Meehan, iGAS Typing Service, Epidemiology and Molecular Biology Unit (EMBU), Children’s University Hospital, Temple Street, Dublin 1

Enhanced surveillance provides valuable information on clinical presentation, severity, risk factors and outcome at 7 days of iGAS cases. Microbiologists and/or public health staff are kindly asked to complete an enhanced iGAS surveillance form (available at: http://www.hpsc.ie/A-Z/Other/GroupAStreptococcalDiseaseGAS/SurveillanceForms/) and submit this to their local public health department.

Guidance for the management of iGAS infections is available on the HPSC website: http://www.hpsc.ie/A-Z/Other/GroupAStreptococcalDiseaseGAS/Guidance/

 
Stephen Murchan¹, Karen Burns¹, Mary Meehan², Sarah Hennessy¹, Robert Cunney<sup>1,2  

1</sup>HPSC, ²Temple St Children’s University Hospital