Invasive group a streptococcal disease in children and association with varicella-zoster virus infection

Objectives. To describe the incidence and clinical features of invasive gro up A streptococcal (GAS) disease in children in Ontario and determine the r isk of invasive GAS infection following chickenpox. Methods. During 1992-1996, we conducted prospective, active, population-bas ed surveillance for pediatric invasive GAS disease in Ontario, Canada (popu lation: 11 million; 2.5 million children) and reviewed clinical and laborat ory 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 in terval [CI]: 2.4-45). Fifteen percent of children identified had preceding chickenpox infection, which significantly increased the risk for acquisitio n of invasive GAS disease (RR: 58; 95% CI: 40-85). Children with invasive G AS 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. Chi ckenpox dramatically increases the risk for acquiring invasive GAS disease, and universal chickenpox vaccination could potentially prevent up to 15% o f all pediatric invasive GAS disease.