Invasive Group A Streptococcal Disease in Children and Association With Varicella-Zoster Virus Infection

Objectives. To describe the incidence and clinical features of invasive group A streptococcal (GAS) disease in children in Ontario and determine the risk of invasive GAS infection following chickenpox. Methods. During 1992–1996, we conducted prospective, active, population-based surveillance for pediatric invasive GAS disease in Ontario, Canada (population: 11 million; 2.5 million children) and reviewed clinical and laboratory records. Results. There were 1.9 cases of invasive GAS disease per 100 000 children per year. Streptococcal toxic shock syndrome (STSS) occurred in 7% of cases and necrotizing fasciitis (NF) in 4% for incidences of .08 and .13 per 100 000 per year, respectively. Case-fatality rates were 56% for STSS, 10% for NF, and 4% overall. The presence of chronic underlying illness other than asthma was associated with death (relative risk [RR]: 11; 95% confidence interval [CI]: 2.4–45). Fifteen percent of children identified had preceding chickenpox infection, which significantly increased the risk for acquisition of invasive GAS disease (RR: 58; 95% CI: 40–85). Children with invasive GAS and recent chickenpox were more likely to have NF (RR: 6.3; 95% CI: 1.8–22.3). Conclusions. Childhood invasive GAS disease occurs at an incidence similar to the adult population but has a lower rate of STSS and case-fatality. Chickenpox dramatically increases the risk for acquiring invasive GAS disease, and universal chickenpox vaccination could potentially prevent up to 15% of all pediatric invasive GAS disease. Pediatrics 2000;105(5). URL: http://www. pediatrics.org/cgi/content/full/105/5/e60; varicella, group A streptococcus, pediatric, risk. ABBREVIATIONS. GAS, group A streptococcus/streptococcal; NF, necrotizing fasciitis; STSS, streptococcal toxic shock syndrome; VZV, varicella-zoster virus; RR, relative risk; CI, confidence interval; IL, interleukin. The past 15 years have witnessed a striking resurgence in the incidence and severity of infections caused by group A streptococci (GAS), including necrotizing fasciitis (NF) and the streptococcal toxic shock syndrome (STSS).1–9 Numerous hospital-based case series have been reported on the clinical spectrum of pediatric invasive GAS disease and have identified that varicella-zoster virus (VZV) infection commonly precedes these infections, especially in cases of NF.10–21 However, to adequately define the epidemiology of these infections, population-based studies are required. Published reports from population-based surveillance of invasive GAS infection have included relatively few pediatric cases.3,5 This limits conclusions regarding the incidence and clinical features of this disease in children. Our group previously reported the results of prospective, population-based surveillance for invasive GAS disease in Ontario, Canada, in 1992–1993, identifying 323 cases of which only 81 were in children.3 The objective of this study was to describe the incidence and clinical features of invasive GAS disease in children in a large population (Ontario) and to better quantify the risk of this disease following chickenpox infection.