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E. COLI EHEC - USA (19): (UTAH, ARIZONA) O157, 2017

Dear Colleagues,
We would like to bring to your attention a report of an outbreak of STEC O157. The event, occurred one year ago, was triggered by environmental exposure to the bug and continued through person-to-person contacts.


E. COLI EHEC - USA (19): (UTAH, ARIZONA) O157, 2017

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A ProMED-mail post <http://www.promedmail.org> ProMED-mail is a program of the International Society for Infectious Diseases <http://www.isid.org>

Date: Thu 14 Jun 2018
Source: MMWR [edited] <https://www.cdc.gov/mmwr/volumes/67/wr/mm6723a2.htm?s_cid=mm6723a2_w>


_E. coli_ O157:H7 Infections Associated with Exposure to Animal Manure in a Rural Community -- Arizona and Utah, June-July 2017
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On 26 Jun 2017, a hospital in southern Utah notified the Utah Department of Health of Shiga toxin-producing _Escherichia coli_ (STEC) [also referred to as enterohemorrhagic _E. coli_ - EHEC - Mod.LL] O157:H7 infections in 2 children from a small community on the Arizona-Utah border. Both children developed hemolytic uremic syndrome, characterized by hemolytic anemia, acute kidney failure, and thrombocytopenia and died within a few days of illness onset. Over the next few days, several more EHEC-associated illnesses were reported in residents of the community. A joint investigation by local and state health agencies from Arizona and Utah and CDC was initiated to identify the outbreak source and prevent additional cases; a total of 12 cases were identified, including the 2 children who died. Investigators initially explored multiple potential sources of illness; epidemiologic and environmental information revealed cow manure contact as the likely initial cause of the outbreak, which was followed by subsequent person-to-person transmission. One of the outbreak strains was isolated from bull and horse manure collected from a yard near a community household with 2 ill children. Local health agencies made recommendations to the public related to both animal contact and hand hygiene to reduce the risk for EHEC transmission. Animal or animal manure contact should be considered a potential source of EHEC O157:H7 during outbreaks in communities where ruminants are kept near the home.

Epidemiologic Investigation
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A case of EHEC O157:H7 infection was defined as an illness in a resident of the Centennial Park/Colorado City/Hildale community with onset of diarrhea after 1 Jun 2017, with 1) culture-confirmed EHEC O157:H7 with one of three novel pulsed-field gel electrophoresis (PFGE) pattern combinations or 2) physician-diagnosed postdiarrheal hemolytic uremic syndrome. Cases were classified as secondary if contact with another case occurred 3 or more days before illness onset. Local health care facilities identified potential cases via syndromic surveillance and reported them to the Southwest Utah Public Health Department and the Mohave County (Arizona) Health Department. The Southwest Utah Public Health Department created several social media posts advising community residents with diarrhea to see a doctor because local health officials were concerned that adults in this community would not seek health care for themselves.

12 cases were identified, including 5 classified as secondary, from 8 separate households. Illness onset dates for the 12 patients ranged from 10 Jun 2018 to 9 Jul 2017 (Figure 1 [for figures and table, see original URL - Mod.LL]). The median age of patients was 3 years (range equal to 1-28 years), and 11 were aged 6 years or older. Five cases occurred in females; 9 patients were hospitalized, 4 had hemolytic uremic syndrome, and 2 died.

All patients or their guardians were interviewed using a hypothesis-generating questionnaire containing questions about foods eaten, food source locations, travel, recreational water exposure, sources of drinking water, and animal contact during the week before illness onset. All 12 patients or their guardians reported shopping at grocery store A, and guardians of 6 of 7 patients with primary cases reported purchasing ground beef. The prevalence of ground beef consumption was significantly higher than that reported in the Foodborne Diseases Active Surveillance Network Population Survey (FoodNet; <https://www.cdc.gov/foodnet/index.html>) (86 percent versus 40 percent; p equal to 0.04) (1); however, local health officials suspected a higher typical ground beef consumption rate in this community than in the nation overall. Thus, other potential hypotheses were explored in a focus group discussion with 5 guardians of 4 ill children. Beef and watermelon consumption, contact with domestic and companion animals, and multiple exposures to recreational water emerged as common exposures.

A 1:3 matched case-control study was designed based on information from the focus group discussion. Guardians of 16 healthy children were recruited through an online survey posted to a closed Facebook group of current and past community residents. The voluntary survey included screening questions to determine their children's eligibility for participation. Community health workers used a focused questionnaire containing questions about consumption of ground beef and fresh produce, as well as all animal contact during the exposure period to interview the guardians of 6 of 7 patients with primary cases and guardians of 16 healthy age-matched controls. 3 of 6 ill children and three of 16 controls reported playing in an area that had animal manure (matched odds ratio equal to 7.7; 95 percent confidence interval equal to 0.8-71.3) (Table).

Contact tracing identified friendships, working relationships, or familial relationships between persons in all 8 households. Illness onset dates were consistent with hypothesized person-to-person contact (Figure 2). The 3 patients with the earliest illness onset dates (patients A, B, and C), including the 2 patients who died, lived in the same multifamily household with approximately 40 persons. After the 2nd patient died, the house was voluntarily vacated, and many persons moved within the community. Contact with animal manure was the hypothesized source of the initial illnesses, with further spread via secondary person-to-person transmission.

Laboratory Investigation
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Officials from the Utah Department of Health and the Mohave County (Arizona) Health Department collected food, water, animal feed and manure, and environmental samples from various locations in the community. The Utah Public Health Laboratory and Arizona State Public Health Laboratory tested 143 samples for EHEC.

A total of 35 samples from grocery store A included ground beef and environmental samples from the meat grinder, meat preparation areas, and meat storage areas. Officials also collected samples of frozen ground beef from households and samples of animal manure from cattle (23), goats (5), horses (17), dogs (11), and other animals (6) in the Centennial Park/Colorado City/Hildale community. Drinking and recreational water samples (12) were collected from surrounding farms and creeks. Stool specimens were obtained from 11 patients.

EHEC was not isolated from any of the food or environmental samples from grocery store A. However, EHEC was isolated from the 11 patient specimens and 3 animal manure samples (2 horses and 1 bull). All isolates were further characterized by whole genome sequencing. Bioinformatic analysis (2) performed at the Utah Public Health Laboratory indicated the 11 clinical isolates, 1 bull manure isolate, and 2 horse manure isolates formed a single monophyletic clade with short branch lengths and high statistical support based on bootstrap statistical analysis of 1000 replicates. This finding indicated that all the isolates were highly related genetically and shared a common molecular evolutionary history. High-quality single-nucleotide polymorphism (hqSNP) analysis performed at CDC (3) indicated that the 11 clinical isolates, 1 bull manure isolate, and 2 horse manure isolates differed by 0-4 hqSNPs, suggesting that they were highly related genetically. EHEC O157:H7 was not isolated from samples from the source farms or animal feed.

Public Health Response
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This multijurisdictional investigation involved daily collaboration among national, state, and local agencies facilitated by an incident command structure. Public communication and educational materials were developed by the Southwest Utah Public Health Department and disseminated by investigation partners, including a public health nurse who was a member of the community. Educational information focused on hygiene related to livestock, safe cooking, increased vigilance for gastrointestinal symptoms, and prevention of secondary transmission. No additional EHEC cases with the outbreak strain have been reported from this community since the conclusion of the investigation.

Discussion
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In this outbreak, playing in an area with animal manure was associated with illness. The 5 ill children with the earliest illness onset dates lived in close proximity to one another and the culture-positive animal manure. EHEC can be shed intermittently by colonized animals, so additional animals might have carried the outbreak strain despite the lack of isolation from manure. Unlike ruminants, horses are not considered reservoirs for EHEC O157:H7 (4,5). The hypothesis is that the 2 horses were infected with the outbreak strain while living in proximity to the bull.

This investigation highlights the use of multiple epidemiologic methods, including hypothesis-generating questionnaires, focus group interviewing, a case-control study, and contact tracing in concert with environmental and clinical testing in identifying the source of an outbreak. These methods were used to generate and test hypotheses regarding four modes of disease transmission: person-to-person, food, drinking and recreational water, and animal contact.

This investigation also highlights the importance of communication and outreach efforts to successful, sensitive public health investigations. The inclusion of a local public health nurse in the investigation team enhanced communication and facilitated both the focus group and contact tracing efforts within a community that had been wary of government officials during previous public health interventions.

The findings in this report are subject to at least three limitations. 1st, this outbreak spread through secondary person-to-person transmission, limiting the number of primary cases available for assessment of exposure frequencies for hypothesis generation. 2nd, for all methods used to investigate hypotheses, ill children or their guardians were contacted 1-6 weeks after the illness began, which could have resulted in inaccurate recall of food and animal contact. Finally, low health care utilization among members of the adult population might have resulted in unidentified cases. These limitations might have decreased the likelihood of statistically significant epidemiologic findings despite positive identification of the outbreak strain in animal manure.

Based on the epidemiologic and environmental data, it is likely that the initial source of this outbreak was contact with animals or their environments. Certain behaviors in the patients with primary cases might have contributed to initiation of the outbreak, such as lack of awareness of the risk for disease, inadequate hand washing, and hand-to-mouth behaviors. Subsequent person-to-person transmission resulted in a large, severe outbreak that included challenges in identifying the source. Strong multijurisdictional partnerships and a combination of epidemiologic methods were necessary to identify an outbreak source. Promoting adequate sanitation and hand washing practices around animal and manure exposure is critical to prevent future outbreaks.

References
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1. CDC: Foodborne Diseases Active Surveillance Network (FoodNet) population survey atlas of exposure, 2006-2007. Atlanta, GA: US Department of Health and Human Services, CDC; 2008. <https://www.cdc.gov/foodnet/surveys/foodnetexposureatlas0607_508.pdf>
2. Oakeson KF, Wagner JM, Mendenhall M, Rohrwasser A, Atkinson-Dunn R: Bioinformatic analyses of whole-genome sequence data in a public health laboratory. Emerg Infect Dis 2017;23:1441-1445.
3. Katz LS, Griswold T, Williams-Newkirk AJ, et al: A comparative analysis of the Lyve-SET phylogenetics pipeline for genomic epidemiology of foodborne pathogens. Front Microbiol 2017;8:375.
4. Lengacher B, Kline TR, Harpster L, Williams ML, Lejeune JT: Low prevalence of _Escherichia coli_ O157:H7 in horses in Ohio, USA. J Food Prot 2010;73:2089-2092.
5. Williams AP, McGregor KA, Killham K, Jones DL: Persistence and metabolic activity of Escherichia coli O157:H7 in farm animal faeces. FEMS Microbiol Lett 2008;287:168-173.

[Authors: Luna S, Krishnasamy V, Saw L, et al]

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Communicated by: ProMED-mail <promed@promedmail.org>

[ProMED posted on this outbreak of EHEC disease in the southwestern USA. The report highlights the need for strict attention to the primary cases to assess the vehicle for transmission. As noted in the posting, horses are rarely linked to human EHEC cases. - Mod.LL

HealthMap/ProMED-mail maps:
Utah, United States: <http://healthmap.org/promed/p/246>
Arizona, United States: <http://healthmap.org/promed/p/207>]

[See Also:
E. coli EHEC - USA (18): (TN) raw milk, more cases http://promedmail.org/post/20180614.5856110
E. coli EHEC - USA (17): (OR) O111, daycare center http://promedmail.org/post/20180613.5854733
E. coli EHEC - USA (16): (TN) raw milk http://promedmail.org/post/20180607.5844304
E. coli EHEC - USA (15): O157, romaine lettuce, more cases, fatal http://promedmail.org/post/20180604.5837662
E. coli EHEC - USA (14): (WA) sandwich shops http://promedmail.org/post/20180527.5820803
E. coli EHEC - USA (13): O157, romaine lettuce, increasing cases, fatality http://promedmail.org/post/20180517.5799620
E. coli EHEC - USA (12): O157, romaine lettuce, increasing cases, fatality http://promedmail.org/post/20180510.5791677
E. coli EHEC - USA (11): (OK) day care center http://promedmail.org/post/20180502.5780250
E. coli EHEC - USA (10): O157, romaine lettuce, fatality http://promedmail.org/post/20180502.5780249
E. coli EHEC - USA (09): O157, romaine lettuce http://promedmail.org/post/20180427.5771229
E. coli EHEC - USA (08): (CA) military outbreak, undercooked beef, 2017 http://promedmail.org/post/20180425.5769489
E. coli EHEC - USA (07): O157, romaine lettuce http://promedmail.org/post/20180425.5769488
E. coli EHEC - USA (06): O157, romaine lettuce http://promedmail.org/post/20180421.5761217
E. coli EHEC - USA (05): O157, romaine lettuce http://promedmail.org/post/20180418.5756056
E. coli EHEC - USA (04): O157, romaine lettuce http://promedmail.org/post/20180413.5745944
E. coli EHEC - USA (03): O157, expansion of NJ outbreak http://promedmail.org/post/20180411.5738813
E. coli EHEC - USA (02): (NJ) poss. restaurant chain link, RFI http://promedmail.org/post/20180405.5728398
E. coli EHEC - USA: O157, leafy greens http://promedmail.org/post/20180110.5550773

2017
---
E. coli EHEC - USA (39): relatedness to Canada isolates http://promedmail.org/post/20171229.5527271
E. coli EHEC - Canada (14): O157, lettuce, fatal http://promedmail.org/post/20171222.5518867
E. coli EHEC - Canada (13): O157, lettuce, fatal http://promedmail.org/post/20171215.5506384
E. coli EHEC - Canada (12) : O157, lettuce http://promedmail.org/post/20171212.5497097
E. coli EHEC - USA (38): (CA) http://promedmail.org/post/20171212.5498214
E. coli EHEC - USA (37): raw dough, FDA alert http://promedmail.org/post/20171202.5479176
E. coli EHEC - USA (36): (CA) military outbreak, O157 http://promedmail.org/post/20171111.5436982
E. coli EHEC - USA (35): (CA) military outbreak, O157 http://promedmail.org/post/20171104.5424631
E. coli EHEC - USA (34): (CA) military outbreak, O157 http://promedmail.org/post/20171103.5422415
E. coli EHEC - USA (33): (CA) military outbreak, O157 http://promedmail.org/post/20171102.5421203
E. coli EHEC - USA (32): (CA) military outbreak, revised case numbers http://promedmail.org/post/20171102.5420166
E. coli EHEC - USA (31): (CA) military outbreak http://promedmail.org/post/20171101.5417972
E. coli EHEC - USA (30): (CA) military outbreak, RFI http://promedmail.org/post/20171031.5416569
E. coli EHEC - USA (29): (MI) farm animal exposures, RFI http://promedmail.org/post/20171030.5410350
E. coli EHEC - USA (28): (VT) O157, ground beef, alert, recall http://promedmail.org/post/20171014.5381117
E. coli EHEC - USA (27): (WI) O157, RFI http://promedmail.org/post/20170921.5330484
E. coli EHEC - USA (26): (MI) O157, antimicrobial resistance http://promedmail.org/post/20170824.5272308
E. coli EHEC - USA (25): (CA) O157, recreational water http://promedmail.org/post/20170818.5258783
E. coli EHEC - USA (24): (CO) county fair, RFI http://promedmail.org/post/20170811.5243577
E. coli EHEC - USA (23): (CA) recreational water http://promedmail.org/post/20170810.5240983
E. coli EHEC - USA (22): (CA) recreational water http://promedmail.org/post/20170804.5227891
E. coli EHEC - USA (21): (CA) recreational water http://promedmail.org/post/20170802.5220799
E. coli EHEC - USA (20): (CA) recreational water, RFI http://promedmail.org/post/20170731.5217061
E. coli EHEC - USA (19): (UT, AZ) O157, fatalities, susp. livestock exposure http://promedmail.org/post/20170730.5215421
E. coli EHEC - USA (18): (UT, AZ) O157, fatalities http://promedmail.org/post/20170727.5206988
E. coli EHEC - USA (17): (OH) summer camp, RFI http://promedmail.org/post/20170724.5198725
E. coli EHEC - USA (16) : (MN) fatality http://promedmail.org/post/20170721.5195217
E. coli EHEC - USA (15): (UT) O157, fatalities http://promedmail.org/post/20170711.5167176
E. coli EHEC - USA (14): (UT) O157, fatalities http://promedmail.org/post/20170705.5152059
E. coli, EHEC - USA (13): (UT) fatalities, susp EHEC, RFI http://promedmail.org/post/20170703.5147181
E. coli EHEC - USA (12): (TX) http://promedmail.org/post/20170621.5121066
E. coli EHEC - USA (11): O157, deer droppings, water exposure, 2016 http://promedmail.org/post/20170511.5028649
E. coli EHEC - USA (10): O157, soynut butter http://promedmail.org/post/20170505.5014128
E. coli EHEC - USA (09): (AR) fatality, unrelated cases http://promedmail.org/post/20170422.4988037
E. coli EHEC - USA (08): (AR) fatality, RFI http://promedmail.org/post/20170421.4984124
E. coli EHEC - USA (07): (MA) O157, restaurant chain, RFI http://promedmail.org/post/20170414.4970974
E. coli EHEC - USA (06): O157, soynut butter http://promedmail.org/post/20170405.4949992
E. coli EHEC - USA (05): O157, soynut butter, CDC update http://promedmail.org/post/20170401.4941247
E. coli EHEC - USA (04): (OR) O157, soynut butter, preschool http://promedmail.org/post/20170315.4902827
E. coli EHEC - USA (03): O157, soynut butter, more cases, recall http://promedmail.org/post/20170308.4887992
E. coli EHEC - USA (02): O157, soynut butter http://promedmail.org/post/20170307.4883675
E. coli EHEC - USA http://promedmail.org/post/20170302.4875298]

Published 27-09-2017 in Focus on , last update 26-06-2018

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