Epidemiology of Invasive Group A Streptococcal Disease in Alaska, 2001 to 2013

Abstract

The Arctic Investigations Program (AIP) began surveillance for invasive group A streptococcal (GAS) infections in Alaska in 2000 as part of the invasive bacterial diseases population-based laboratory surveillance program. Between 2001 and 2013, there were 516 cases of GAS infection reported, for an overall annual incidence of 5.8 cases per 100,000 persons with 56 deaths (case fatality rate, 10.7%). Of the 516 confirmed cases of invasive GAS infection, 422 (82%) had isolates available for laboratory analysis. All isolates were susceptible to penicillin, cefotaxime, and levofloxacin. Resistance to tetracycline, erythromycin, and clindamycin was seen in 11% (n = 8), 5.8% (n = 20), and 1.2% (n = 4) of the isolates, respectively. A total of 51 emm types were identified, of which emm1 (11.1%) was the most prevalent, followed by emm82 (8.8%), emm49 (7.8%), emm12 and emm3 (6.6% each), emm89 (6.2%), emm108 (5.5%), emm28 (4.7%), emm92 (4%), and emm41 (3.8%). The five most common emm types accounted for 41% of isolates. The emm types in the proposed 26-valent and 30-valent vaccines accounted for 56% and 78% of all cases, respectively. GAS remains an important cause of invasive bacterial disease in Alaska. Continued surveillance of GAS infections will help improve understanding of the epidemiology of invasive disease, with an impact on disease control, notification of outbreaks, and vaccine development.

FIG 1

Incidence rates and numbers of cases of invasive group A streptococcal disease by year in Alaska, 2001 to 2013.

FIG 2

Distribution of emm types among invasive group A streptococcal isolates in Alaska by time period, 2001 to 2006, 2006 to 2009, and 2010 to 2013. Asterisks indicate emm types present in both the 26-valent and 30-valent vaccines. emm types present in the 30-valent but not in the 26-valent vaccine include types 82, 49, 87, 73, 58, 44, 83, 4, and 118. emm types contained in the 26-valent but not in the 30-valent include types 76, 94, and 101. emm types that are not included in either vaccine are types 108, 41, and 1-2.3.