The changing epidemiology of invasive group A streptococcal infections and the emergence of streptococcal toxic shock-like syndrome. A retrospective population-based study

Abstract

Objective: To determine disease incidence and changes in the epidemiology of invasive group A streptococcal infections in a community in Arizona.

Design and setting: We retrospectively surveyed microbiology records from all 10 hospitals in Pima County, Arizona, to identify patients who had Streptococcus pyogenes isolated from blood, sterile body fluid, or tissue biopsy specimens between April 1985 and March 1990. Demographic and clinical information was abstracted from the medical records of these patients.

Patients: A total of 128 patients with a median age of 53.5 years (range, 6 months to 96 years).

Outcome measures: Racial/ethnic differences in disease incidence; mortality and changes in the clinical spectrum of disease over the study period.

Results: The annual age-adjusted incidence was 4.3 per 100,000 but was 46.0 per 100,000 among Native Americans. Advanced age, age less than 5 years, hypotension, and multi-organ system involvement were significantly associated with increased mortality. From 1985 to 1990, the proportion of infections with hypotension, rash, desquamation, renal impairment, and gastrointestinal involvement increased significantly (chi 2 for trend P < or = .02 for each feature). A toxic shock-like syndrome occurred in 8% of infections since 1988, compared with none of the infections between 1985 and 1987 (P = .04). Patients with the syndrome were younger than patients with other invasive infections (median age 15 vs 54 years, P = .02), and were less likely to have underlying medical conditions (P = .008).

Conclusions: Significant changes occurred in the spectrum of invasive group A streptococcal infections in Pima County, Arizona, between 1985 and 1990. Native Americans were at increased risk of acquiring these infections. Patients with the streptococcal toxic shock-like syndrome had epidemiologic features that distinguished them from patients with other invasive infections, including younger age and less underlying illness.