E. coli O157:H7 From Animal Manure: 12 Ill, 2 Children Dead, Arizona–Utah Border, 2017

On June 26, 2017, a hospital in southern Utah reported Shiga toxin–producing E. coli (STEC) O157:H7 infections in two children from a small community on the Arizona–Utah border. Both developed hemolytic uremic syndrome — hemolytic anemia, acute kidney failure and thrombocytopenia — and died within days. More cases followed, and local and state health agencies from Arizona and Utah and CDC set out to find the source.

The outbreak

A case was an illness from June 1, 2017, in a resident of Centennial Park, Colorado City or Hildale, confirmed as STEC O157:H7 with one of three new genetic fingerprint patterns (PFGE) or diagnosed as hemolytic uremic syndrome after diarrhea.

• 12 cases in 8 households, with illness beginning June 10 to July 9; 5 were secondary (caught from another patient).
• Median age 3 (range 1–28); 11 were 6 or younger; 5 were female.
• 9 hospitalized, 4 with hemolytic uremic syndrome, 2 deaths.
• Worried that adults in the community would not seek care, the Southwest Utah Public Health Department used social media to urge anyone with diarrhea to see a doctor.

Figure 1. Cases by date of illness onset, Centennial Park/Colorado City/Hildale, June–July 2017. CDC.

Following the clues

Food first. All 12 patients' families shopped at grocery store A, and six of seven families of primary patients had bought ground beef — 86%, against 40% in a national survey. But local officials thought the community ate more ground beef than average anyway.

A focus group of five guardians of four sick children pointed to beef, watermelon, animal contact and recreational water.

A case-control study compared six children with primary cases to 16 healthy children of the same ages:

Contact tracing found friendships, working ties or family links among all eight households, with onset dates fitting person-to-person spread. The first three patients, including the two who died, lived in one multifamily household of about 40 people; after the second death the house was vacated, and many residents moved elsewhere in the community.

Figure 2. Primary and secondary cases by day of the outbreak. CDC.

The laboratory

State public health laboratories tested 143 samples: 35 from grocery store A (ground beef, the grinder, preparation and storage areas), frozen ground beef from homes, manure from cattle (23), goats (5), horses (17), dogs (11) and other animals (6), and 12 drinking and recreational water samples.

• No STEC was found in any sample from the grocery store, or from the source farms or animal feed.
• STEC was found in stool from 11 patients and in three manure samples — two horses and one bull — in a yard near the homes of the first patients.
• Whole genome sequencing showed the 11 patient isolates and the three manure isolates differed by only 0–4 high-quality SNPs — closely related.

Horses, unlike ruminants, are not considered reservoirs of O157:H7; the likely explanation is that they picked it up living near the bull. Colonized animals shed the bacteria intermittently, so other animals may have carried it too.

Conclusions

The outbreak most likely began with contact with animals or their surroundings — helped perhaps by little awareness of the risk, poor handwashing and hand-to-mouth behavior in young children — and then spread person to person, which made the source hard to find.

• An incident command structure and daily collaboration among federal, state and local agencies drove the investigation.
• A public health nurse from the community joined the team, easing communication, the focus group and contact tracing in a community wary of government officials from earlier interventions.
• Public messages covered livestock hygiene, safe cooking, watching for gastrointestinal symptoms and preventing secondary spread. No further cases were reported.

Lessons: handwashing matters in reducing STEC O157:H7 spread, and animal or manure contact should be considered in outbreaks where ruminants are kept near homes.

Limitations: person-to-person spread left few primary cases to study; families were interviewed 1–6 weeks after illness, so memories may be inaccurate; and adults seldom seek care, so some cases may have been missed.

Sources

Based on Luna S, Krishnasamy V, Saw L, et al., "Outbreak of E. coli O157:H7 Infections Associated with Exposure to Animal Manure in a Rural Community — Arizona and Utah, June–July 2017," MMWR Morbidity and Mortality Weekly Report, volume 67, Centers for Disease Control and Prevention; a work of the United States government in the public domain. The report places the positive manure near "the first seven patients," "a community household with two ill children," and "the five ill children with the earliest illness onset dates" in different sections; no number is given here.