Abstract
Invasive group A streptococcal infections (iGAS) are a major clinical and public health challenge. iGAS is a notifiable disease in Ireland since 2004. The aim of this paper is to describe the epidemiology of iGAS in Ireland for the first time over the seven-year period from 2004 to 2010. The Irish national electronic infectious disease reporting system was used by laboratories to enter the source of iGAS isolates, and by departments of public health to enter clinical and epidemiological details. We extracted and analysed data from 1 January 2004 to 31 December 2010. Over the study period, 400 iGAS cases were notified. The annual incidence of iGAS doubled, from 0.8 per 100,000 population in 2004 to 1.6 in 2008, and then remained the same in 2009 and 2010. The reported average annual incidence rates were highest among children up to five years of age (2.3/100,000) and adults aged over 60 years (3.2/100,000). The most common risk factors associated with iGAS were skin lesions or wounds. Of the 174 people for whom clinical syndrome information was available, 28 (16%) cases presented with streptococcal toxic shock syndrome and 19 (11%) with necrotising fasciitis. Of the 141 cases for whom seven-day outcomes were recorded, 11 people died with iGAS identified as the main cause of death (seven-day case fatality rate 8%). The notification rate of iGAS in Ireland was lower than that reported in the United Kingdom, Nordic countries and North America but higher than southern and eastern European countries. The reasons for lower notification rates in Ireland compared with other countries may be due to a real difference in incidence, possibly due to prescribing practices, or due to artefacts resulting from the specific Irish case definition and/or low reporting in the early stages of a new surveillance system. iGAS disease remains an uncommon but potentially severe disease in Ireland. Ongoing surveillance is required in order to undertake appropriate control measures and gain a greater understanding of this disease.
Highlights
Invasive group A streptococcal infection occurs when Streptococcus pyogenes invades a normally sterile site, e.g. blood, cerebrospinal fluid (CSF) or pleural fluid, and is associated with severe disease including necrotising fasciitis (NF), meningitis and streptococcal toxic shock syndrome (STSS) [1]. iGAS is relatively uncommon, the rapidity with which patients deteriorate, its occurrence in otherwise healthy people and the difficulties in the differential diagnosis underlie the importance of surveillance of this disease
The highest incidence annually was between late December and late August but this was not statistically significant by individual year or when averaged over seven years (p>0.05), seasonal trends could not be inferred by this study
The incidence of iGAS increased from 0.8 per 100,000 population in 2004 to 1.6 in 2008, after which it stabilised, with the highest age-specific incidence rates seen in children less than five years of age and adults aged 60 years and over
Summary
Invasive group A streptococcal infection (iGAS) occurs when Streptococcus pyogenes invades a normally sterile site, e.g. blood, cerebrospinal fluid (CSF) or pleural fluid, and is associated with severe disease including necrotising fasciitis (NF), meningitis and streptococcal toxic shock syndrome (STSS) [1]. iGAS is relatively uncommon, the rapidity with which patients deteriorate, its occurrence in otherwise healthy people and the difficulties in the differential diagnosis underlie the importance of surveillance of this disease. Surveillance enables early detection of clusters/outbreaks to ensure prompt implementation of infection prevention, and control precautions and appropriate management of contacts. The MOH will undertake/delegate an investigation to identify contacts in order to provide information and prescribe chemoprophylaxis if indicated. Indications are (i) close contacts if they have symptoms suggestive of localised group A streptococcal (GAS) infection or (ii) mother and baby if either develops iGAS in the neonatal period (first 28 days of life). The MOH investigation is to identify outbreaks
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