Epidemiological Changes In Shiga Toxin-Producing Escherichia Coli (stec) Pre- And Post-Covid In Connecticut, 2018–2019 And 2023–2024

Abstract

Background: Shiga toxin-producing Escherichia coli (STEC) causes over 265,000 infections, 3,600 hospitalizations, and 30 deaths annually in the U.S.. While STEC O157 is the most common serotype, the increased use of culture-independent diagnostic tests (CIDT) led to a rise in non-O157 serotypes detected. Nationally, STEC incidence declined during the COVID-19 pandemic but has since surpassed pre-pandemic levels. An analysis was conducted to determine the changes that occurred in STEC infections in Connecticut from pre-pandemic to post-pandemic and to identify differences between culture-confirmed cases and CIDT-only/untyped cases.Methods: A descriptive analysis using STEC surveillance data collected in Connecticut was performed to identify changes in STEC infections, comparing cases reported in 2018–2019 (N = 238) to 2023–2024 (N = 342) by demographic characteristics, testing method, and exposure history. A case-case analysis was conducted among post-pandemic infections to identify differences between serotyped/culture-confirmed cases (N = 126) and CIDT-only/untyped cases (N = 216). Results: The overall incidence of STEC infections increased post-pandemic (RR 1.44, 95% CI 1.22-1.70). Incidence in the Hispanics/Latinos doubled (RR 1.98, 95% CI 1.40-2.79), driven by adults 18-64 years of age, to a rate that was nearly double that of any race/ethnic group. The proportion of culture-confirmed infections halved from pre-pandemic to post-pandemic (OR 0.49, 95% CI 0.35-0.63). Among confirmed infections, O157 decreased (26.9% pre-pandemic to 15.1% post-pandemic) while non-O157 increased (71.5% pre-pandemic to 80.2% post-pandemic). Farm animal exposure increased (OR 4.15, 95% CI 1.20-14.34). CIDT-only infections compared to culture-confirmed infections were 27.0% as likely to have bloody diarrhea (27.0% vs 51.3%) but were just as likely to have HUS and to be hospitalized. CIDT-only cases were also more likely (p\u3c0.05) to be ≥65 years old (29.6% vs 14.3%), less likely to have attended or worked at a daycare (3.3% vs 12.1%), and be outbreak-associated (0% vs 17.5%). Conclusions: STEC incidence increased post-pandemic, driven by a rise in non-O157 serotypes and greater use of CIDT methods, with the most substantial increases among Hispanic/Latino adults and older populations. Changes in incidence highlight the need for continued surveillance