Risk for Severe Group A Streptococcal Disease Among Patients' Household Contacts

Katherine A. Robinson, Gretchen Rothrock, Quyen Phan, Brenda Sayler, Karen Stefonek, Chris Van Beneden, Orin S. Levine

Disclosures

Emerging Infectious Diseases. 2003;9(4) 

In This Article

Abstract and Introduction

From January 1997 to April 1999, we determined attack rates for cases of invasive group A streptococcal (GAS) disease in household contacts of index patients using data from Active Bacterial Core Surveillance sites. Of 680 eligible index-patient households, 525 (77.2%) were enrolled in surveillance. Of 1,514 household contacts surveyed, 127 (8.4%) sought medical care, 24 (1.6%) required hospital care, and none died during the 30-day reference period. One confirmed GAS case in a household contact was reported (attack rate, 66.1/100,000 household contacts). One household contact had severe GAS-compatible illness without confirmed etiology. Our study suggests that subsequent cases of invasive GAS disease can occur, albeit rarely. The risk estimate from this study is important for developing recommendations on the use of chemoprophylaxis for household contacts of persons with invasive GAS disease.

Group A streptococcus (GAS) causes a wide range of illnesses from noninvasive disease such as pharyngitis and pyoderma[1,2] to more severe invasive infections (e.g., bacteremia, pneumonia, and puerperal sepsis).[3,4] In the 1980s, invasive GAS infections received increasing attention from the medical community and the public because of necrotizing fasciitis (NF)[5,6] and the emergence of streptococcal toxic shock syndrome (STSS).[7,8,9,10] Based on results of the Active Bacterial Core Surveillance (ABCs)/Emerging Infections Program network, a population-based surveillance system, the Centers for Disease Control and Prevention (CDC) estimates that, in 1999, the annual invasive GAS incidence was 3.5 cases per 100,000 population, yielding approximately 9,400 cases and 1,200 deaths in the United States that year.[11]

The severity of GAS disease, coupled with a number of case clusters reported in communities and families[12,13,14] and several anecdotal reports of subsequent cases of invasive GAS infection in close contacts, causes concerns about the spread of disease among close contacts and questions about whether chemoprophylaxis to prevent illness in close contacts is warranted. Using data from active surveillance in Ontario, Canada, where the baseline rate of sporadic invasive GAS disease was 2.4 per 100,000 population (pers. comm.), investigators estimated that the attack rate of disease among household contacts of patients with invasive GAS disease was higher than the rate of invasive disease among the general population (294.1/ 100,000 population).[3]

In October 1995, the Working Group on Prevention of Invasive GAS Infections, composed of streptococcal experts from a variety of clinical and public health organizations, CDC, and various academic institutions, held a meeting to examine existing data and to determine if these data were sufficient to recommend widespread use of chemoprophylaxis to prevent subsequent invasive GAS disease among close contacts of index patients. Four specific criteria were used:[15] severity of disease,[16,17,18,19] virulence of the strain,[18,20,21,22,23] increased risk for subsequent disease, and availability of an effective chemoprophylaxis regimen. Both the severity of invasive GAS disease and the virulence of GAS strains had been well documented. However, at that time, limited data existed regarding the risk for subsequent GAS disease among household contacts and an optimal regimen for chemoprophylaxis.

The working group concluded that a single study with four case-pairs was inadequate for establishing national recommendations for chemoprophylaxis for subsequent invasive GAS illness and emphasized the need for additional data on the risk of subsequent GAS disease among household contacts.[15] We conducted surveillance to quantify the subsequent attack rates for both confirmed invasive GAS disease and severe GAS-compatible disease with no known etiology among household contacts in four geographic areas in the United States.

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