Invasive Group A Streptococcal Infections Among People Who Inject Drugs and People Experiencing Homelessness in the United States, 2010-2017

Background. Reported outbreaks of invasive group A Streptococcus (iGAS) infections among people who inject drugs (PWID) and people experiencing homelessness (PEH) have increased, concurrent with rising US iGAS rates. We describe epidemiology among iGAS patients with these risk factors. Methods. We analyzed iGAS infections from population-based Active Bacterial Core surveillance (ABCs) at 10 US sites from 2010 to 2017. Cases were defined as GAS isolated from a normally sterile site or from a wound in patients with necrotizing fasciitis or streptococcal toxic shock syndrome. GAS isolates were emm typed. We categorized iGAS patients into four categories: injection drug use (IDU) only, homelessness only, both, and neither. We calculated annual change in prevalence of these risk factors using log binomial regression models. We estimated national iGAS infection rates among PWID and PEH. Results. We identified 12 386 iGAS cases; IDU, homelessness, or both were documented in similar to 13%. Skin infections and acute skin breakdown were common among iGAS patients with documented IDU or homelessness. Endocarditis was 10-fold more frequent among iGAS patients with documented IDU only versus those with neither risk factor. Average percentage yearly increase in prevalence of IDU and homelessness among iGAS patients was 17.5% and 20.0%, respectively. iGAS infection rates among people with documented IDU or homelessness were similar to 14-fold and 17- to 80-fold higher, respectively, than among people without those risks. Conclusions. IDU and homelessness likely contribute to increases in US incidence of iGAS infections. Improving management of skin breakdown and early recognition of skin infection could prevent iGAS infections in these patients.