Connecticut Epidemiologist Newsletter   •  November 2023   •   Volume 43, No 8
 

First Known Outbreak of E. Coli (ETEC) in Connecticut, May 2022

Background

In May 2022, the Connecticut Department of Public Health (DPH) was notified of a possible foodborne outbreak among attendees of two luncheons. The events were catered by the same food service establishment (FSE). Both luncheons occurred on May 4th, 2022; sixty individuals attended Event A and sixteen attended Event B. Other complaints of illness were received from patrons of the same FSE who ordered take-out for a private party (Event C) on May 3rd, 2022. Staff from the DPH Epidemiology and Emerging Infections Program, the Yale Emerging Infections Program, the DPH Food Protection Program (FPP), and the local health department (LHD) performed a joint investigation to implement control measures and investigate the extent and cause of illnesses. This report summarizes the investigation’s epidemiologic, environmental, and laboratory findings.

Epidemiological Investigation

A cohort study was conducted among luncheon attendees. DPH epidemiologists created a standardized questionnaire in SurveyMonkey®, which assessed symptom and exposure information. Of the 76 total luncheon attendees, 54 (71%) completed the survey: 49 of 60 (82%) from Event A and 5 of 16 (31%) from Event B. Seventeen responses were excluded due to incompleteness (14) or pre-existing gastrointestinal symptoms (3), leaving 37 surveys for analysis. A case-patient was defined as an individual with no prior gastrointestinal illness who ate food from the luncheons and experienced diarrhea (≥3 stools in a 24-hour period) within three days. In total, 26 case-patients were identified (Event A: 24, Event B: 2).

Food consumption analysis suggested that ingestion of sour cream was associated with illness (Relative Risk= 2.00, 95% CI: 1.26-3.17, p<0.01). There was a 100% (10/10) attack rate among those who reported sour cream consumption, compared to 50% (9/18) among those who did not report sour cream. No other menu items were significantly associated with illness (Table 1).                                                                                                                                                                                                                                                    Staff were only able to interview one attendee of Event C, who reported that 3 of the 4 patrons became ill after the event. The attendee reported that ill patrons experienced symptoms including diarrhea, vomiting, and fever. Without direct interviews, the case definition criteria and consumption of specific foods, including sour cream, could not be ascertained; these patrons were excluded from the cohort analysis.

Environmental Investigation

On May 9th, LHD staff visited the FSE. The team at the FSE interviewed 15 food workers (FWs) engaged in food preparation, provided stool collection kits for FWs, and collected information on the food items served, food handling procedures, catering invoices, and FW contact information. Only one FW reported symptoms; this FW worked on May 2nd and May 4th, prepared the guacamole for the event, later experienced diarrhea on May 8th, and came to work the following day.

The LHD did not observe any hot or cold temperature holding issues. There was documentation of employee training which included the policy that employees should not work if ill; however, a poster intended to remind FWs to abstain from work while sick was not posted. Food items were prepared up to 2 days before catered events, packaged on trays or in containers, transported in insulated bags, delivered to the sites, and set up for self-service. Hot food was set up with chafing dishes.

DPH FPP staff visited the FSE on May 11th for an Environmental Assessment. Though under ownership of someone with other establishments, this FSE opened a few weeks prior to the events. Thus, there was no inspection history to review. All holding and cooking temperatures met required levels with no signs of contamination. Staff were observed wearing gloves when handling ready-to-eat foods and following proper procedure for changing gloves and handwashing. Contributing factors could not be determined for this outbreak.

Laboratory Investigation

Stool specimens were collected from luncheon attendees (9), a private party attendee (1), and FWs (13). Samples were tested using the BioFire GI panel at the CT DPH State Laboratory. In total, eight patrons (7 luncheon attendees, 1 private party attendee) and five FWs tested positive for ETEC; these samples were sent to the Minnesota Department of Public Health Laboratory (MN DPHL) for culture testing and whole genome sequencing (WGS).

The symptomatic FW tested positive for ETEC at CT DPHL, but the sample did not get forwarded to MN DPHL. Instead, one FW sample initially negative for ETEC was inadvertently sent to MN DPHL, where it tested positive via their lab-developed PCR test and culture. In total, MN DPHL isolated ETEC from 9 of 13 specimens (5 luncheon attendees, 1 private party attendee, 3 FWs). All 9 were serotyped as O169/O183:H41 and were highly related. No environmental samples were tested.

Discussion

In the United States, ETEC is well-understood as a cause of traveler’s diarrhea, but domestically acquired cases may be becoming more prevalent (1). Analysis by MN DPH found only 43% of ETEC cases had recently traveled internationally (1). ETEC are gram-negative bacteria known to produce heat-labile toxin (HT) and heat-stable toxin (ST); one or both toxins may be produced, which contributes to varying illness severity, ranging from mild diarrhea to cholera-like illness characterized by loose, watery stools (2,3).

This investigation of illnesses among patrons of an FSE in May 2022 marked the first known outbreak of ETEC in Connecticut. Consumption of sour cream at the luncheons was statistically associated with illness, but it remains unknown if this was the true food vehicle or how it may have become contaminated. Raw fruits and vegetables are considered high risk foods for domestically acquired ETEC (1,4); pasteurized dairy products are not common sources of infection (4). There were no factors identified from environmental investigations that suggested improper food handling or temperature control practices.

These findings highlight the importance of considering ETEC as an etiologic agent of domestic gastroenteritis outbreaks. Continued surveillance for ETEC is necessary to strengthen the understanding of domestically acquired ETEC risk factors and identify opportunities for prevention.

Reported by

Morris, MPH, N Bramlitt, MPH, T Rissman, MPH, Yale Emerging Infections Program; E Flaherty, BS, C Turner, MPH, Q Phan, MPH, Epidemiology and Emerging Infections Program; C Nishimura, MPH, D Santoro, BS, Connecticut Department of Public Health State Public Health Laboratory; M Payne, MPH, REHS/RS, T Weeks, MS RS, C Costa, RS, Food Protection Program; Local Health Department Staff

References

1. Buuck S, Smith K, Fowler RC, Cebelinski E, Lappi V, Boxrud D, Medus C. Epidemiology of Enterotoxigenic Escherichia coli infection in Minnesota, 2016-2017. Epidemiol Infect. 2020 Sep 1;148:e206. doi: 10.1017/S0950268820001934. PMID: 32867880; PMCID: PMC7506794.

2. Wolf, M. K. (1997). Occurrence, distribution, and associations of O and H serogroups, colonization factor antigens, and toxins of enterotoxigenic Escherichia coli. Clinical microbiology reviews, 10(4), 569-584.

3. Nataro, J. P., & Kaper, J. B. (1998). Diarrheagenic escherichia coli. Clinical microbiology reviews, 11(1), 142-201.

4. Centers for Disease Control and Prevention. Enterotoxigenic E. coli (ETEC) Frequently Asked Questions. Published December 1, 2014. Accessed November 9, 2023. https://www.cdc.gov/ecoli/etec.html

This page last updated 12/05/2023