Multistate Outbreak of Escherichia coli O157:H7 Infections Associated with Consumption of Fresh Spinach: United States, 2006.

During September to October, 2006, state and local health departments and the Centers for Disease Control and Prevention investigated a large, multistate outbreak of Escherichia coli O157:H7 infections. Case patients were interviewed regarding specific foods consumed and other possible exposures. E. coli O157:H7 strains isolated from human and food specimens were subtyped using pulsed-field gel electrophoresis and multiple-locus variable-number tandem repeat analyses (MLVA). Two hundred twenty-five cases (191 confirmed and 34 probable) were identified in 27 states; 116 (56%) case patients were hospitalized, 39 (19%) developed hemolytic uremic syndrome, and 5 (2%) died. Among 176 case patients from whom E. coli O157:H7 with the outbreak genotype (MLVA outbreak strain) was isolated and who provided details regarding spinach exposure, 161 (91%) reported fresh spinach consumption during the 10 days before illness began. Among 116 patients who provided spinach brand information, 106 (91%) consumed bagged brand A. E. coli O157:H7 strains were isolated from 13 bags of brand A spinach collected from patients' homes; isolates from 12 bags had the same MLVA pattern. Comprehensive epidemiologic and laboratory investigations associated this large multistate outbreak of E. coli O157:H7 infections with consumption of fresh bagged spinach. MLVA, as a supplement to pulsed-field gel electrophoresis genotyping of case patient isolates, was important to discern outbreak-related cases. This outbreak resulted in enhanced federal and industry guidance to improve the safety of leafy green vegetables and launched an independent collaborative approach to produce safety research in 2007.

Escherichia coli O157:H7 infections associated with consumption of locally grown strawberries contaminated by deer.

BACKGROUND: An outbreak of Escherichia coli O157:H7 was identified in Oregon through an increase in Shiga toxin-producing E. coli cases with an indistinguishable, novel pulsed-field gel electrophoresis (PFGE) subtyping pattern. METHODS: We defined confirmed cases as persons from whom E. coli O157:H7 with the outbreak PFGE pattern was cultured during July-August 2011, and presumptive cases as persons having a household relationship with a case testing positive for E. coli O157:H7 and coincident diarrheal illness. We conducted an investigation that included structured hypothesis-generating interviews, a matched case-control study, and environmental and traceback investigations. RESULTS: We identified 15 cases. Six cases were hospitalized, including 4 with hemolytic uremic syndrome (HUS). Two cases with HUS died. Illness was significantly associated with strawberry consumption from roadside stands or farmers' markets (matched odds ratio, 19.6; 95% confidence interval, 2.9-∞). A single farm was identified as the source of contaminated strawberries. Ten of 111 (9%) initial environmental samples from farm A were positive for E. coli O157:H7. All samples testing positive for E. coli O157:H7 contained deer feces, and 5 tested farm fields had ≥ 1 sample positive with the outbreak PFGE pattern. CONCLUSIONS: The investigation identified fresh strawberries as a novel vehicle for E. coli O157:H7 infection, implicated deer feces as the source of contamination, and highlights problems concerning produce contamination by wildlife and regulatory exemptions for locally grown produce. A comprehensive hypothesis-generating questionnaire enabled rapid identification of the implicated product. Good agricultural practices are key barriers to wildlife fecal contamination of produce.

A norovirus outbreak related to contaminated surfaces.

We investigated an outbreak of norovirus infection affecting 12 of 16 auto dealership employees (75%) subsequent to a staff meeting. Take-out sandwiches initially seemed the likely source, but a cohort study found no association between illness and food consumption. Employees reported seeing a toddler with diarrhea in a dealership restroom shortly before the luncheon. Indistinguishable norovirus was isolated from employees and the child (genotype GII6.C) and from a diaper-changing station in the restroom (genogroup GII). Counterintuitively, this point-source outbreak following a meal was caused by environmental exposures, not food. Environmental exposures should be considered even in routine outbreak investigations.

Outbreak of salmonellosis linked to live poultry from a mail-order hatchery.

BACKGROUND: Outbreaks of human salmonella infections are increasingly associated with contact with live poultry, but effective control measures are elusive. In 2005, a cluster of human salmonella Montevideo infections with a rare pattern on pulsed-field gel electrophoresis (the outbreak strain) was identified by PulseNet, a national subtyping network. METHODS: In cooperation with public health and animal health agencies, we conducted multistate investigations involving patient interviews, trace-back investigations, and environmental testing at a mail-order hatchery linked to the outbreak in order to identify the source of infections and prevent additional illnesses. A case was defined as an infection with the outbreak strain between 2004 and 2011. RESULTS: From 2004 through 2011, we identified 316 cases in 43 states. The median age of the patient was 4 years. Interviews were completed with 156 patients (or their caretakers) (49%), and 36 of these patients (23%) were hospitalized. Among the 145 patients for whom information was available, 80 (55%) had bloody diarrhea. Information on contact with live young poultry was available for 159 patients, and 122 of these patients (77%) reported having such contact. A mail-order hatchery in the western United States was identified in 81% of the trace-back investigations, and the outbreak strain was isolated from samples collected at the hatchery. After interventions at the hatchery, the number of human infections declined, but transmission continued. CONCLUSIONS: We identified a prolonged multistate outbreak of salmonellosis, predominantly affecting young children and associated with contact with live young poultry from a mail-order hatchery. Interventions performed at the hatchery reduced, but did not eliminate, associated human infections, demonstrating the difficulty of eliminating salmonella transmission from live poultry.

A point-source norovirus outbreak caused by exposure to fomites.

We investigated a norovirus outbreak (genotype GII.2) affecting 9 members of a soccer team. Illness was associated with touching a reusable grocery bag or consuming its packaged food contents (risk difference, 0.636; P < .01). By polymerase chain reaction, GII norovirus was recovered from the bag, which had been stored in a bathroom used before the outbreak by a person with norovirus-like illness. Airborne contamination of fomites can lead to subsequent point-source outbreaks. When feasible, we recommend dedicated bathrooms for sick persons and informing cleaning staff (professional or otherwise) about the need for adequate environmental sanitation of surfaces and fomites to prevent spread.

Sapovirus outbreaks in long-term care facilities, Oregon and Minnesota, USA, 2002-2009.

We tested fecal samples from 93 norovirus-negative gastroenteritis outbreaks; 21 outbreaks were caused by sapovirus. Of these, 71% were caused by sapovirus genogroup IV and 66% occurred in long-term care facilities. Future investigation of gastroenteritis outbreaks should include multi-organism testing.

The etiology of severe acute gastroenteritis among adults visiting emergency departments in the United States.

BACKGROUND: Acute gastroenteritis (AGE) remains a common cause of clinic visits and hospitalizations in the United States, but the etiology is rarely determined. METHODS: We performed a prospective, multicenter emergency department-based study of adults with AGE. Subjects were interviewed on presentation and 3-4 weeks later. Serum samples, rectal swab specimens, and/or whole stool specimens were collected at presentation, and serum was collected 3-4 weeks later. Fecal specimens were tested for a comprehensive panel of viral, bacterial, and parasitic pathogens; serum was tested for calicivirus antibodies. RESULTS: Pathogens were detected in 25% of 364 subjects, including 49% who provided a whole stool specimen. The most commonly detected pathogens were norovirus (26%), rotavirus (18%), and Salmonella species (5.3%). Pathogens were detected significantly more often from whole stool samples versus a rectal swab specimen alone. Nine percent of subjects who provided whole stool samples had >1 pathogen identified. CONCLUSIONS: Viruses, especially noroviruses, play a major role as agents of severe diarrhea in adults. Further studies to confirm the unexpectedly high prevalence of rotaviruses and to explore the causes of illness among patients from whom a pathogen cannot be determined are needed. Studies of enteric pathogens should require the collection of whole stool samples.

Specimen collection and confirmation of norovirus outbreaks.

We evaluated data from gastroenteritis outbreaks in Oregon to assess sensitivity of stool testing for norovirus and determine number of specimens needed to confirm norovirus as the cause. Norovirus can be readily confirmed if 3-6 specimens are collected any time ≤7 days after onset of diarrhea and for almost that long after symptoms resolve.

Shigellosis from an interactive fountain: implications for regulation.

In July 2003, the authors investigated an outbreak of Shigella sonnei infections in Marion County, Oregon. Nineteen confirmed and 37 presumptive cases, mostly young children, were identified. A case-control study implicated play in an interactive fountain in a city park (matched odds ratio undefined; p < .002). The association was confirmed by a cohort study among local schoolchildren (RR [relative risk] = 12.6, p < .001) that allowed the authors to estimate that > 500 persons became ill. Fountain design flaws and inadequate maintenance set the stage for the outbreak. In 2007, the authors surveyed state health departments to assess rules and regulations governing interactive fountains. Thirty of 48 states responding (62%) reported public health regulation of fountains; standards and enforcement capacity varied. Regulation is a relatively new phenomenon; only 13 states (27%) had rules before 2000. A lack of enforceable design and maintenance standards increases the risk of enteric disease transmission at these increasingly popular venues.

Comparison of survey methods in norovirus outbreak investigation, Oregon, USA, 2009.

We compared data from an Internet-based survey and a telephone-based survey during a 2009 norovirus outbreak in Oregon. Survey initiation, timeliness of response, and attack rates were comparable, but participants were less likely to complete Internet questions. Internet-based surveys permit efficient data collection but should be designed to maximize complete responses.

Tri-county comprehensive assessment of risk factors for sporadic reportable bacterial enteric infection in children.

BACKGROUND: The aim of this study was to determine risk factors for childhood sporadic reportable enteric infection (REI) caused by bacteria, specifically Campylobacter, Salmonella, Escherichia coli O157, or Shigella (REI-B). METHODS: Matched case-control study. Case patients aged <19 years who were reported to 3 Washington State county health departments and matched control subjects were interviewed from November 2003-November 2005. Matched odds ratios (ORs) were calculated by using conditional logistic regression. Population attributable risk percentages were calculated for exposures associated with infection. RESULTS: Two hundred ninety-six case patients were matched to 580 control subjects. Aquatic recreation was the most important factor associated with all REI-Bs studied (beach water exposure [OR for Salmonella infection, 28.3 {CI, 7.2-112.2}; OR for Shigella infection, 14.5 {CI 1.5-141.0} or any recreational water exposure [OR for Campylobacter infection, 2.7 {CI, 1.5-4.8}; OR for Escherichia coli O157 infection, 7.4 {CI, 2.1-26.1}]). Suboptimal kitchen hygiene after preparation of raw meat or chicken (OR, 7.1 [CI, 2.1-24.1]) and consumption of food from restaurants were additional risks for Campylobacter infection. Infection with Salmonella was associated with the use of private wells as sources of drinking water (OR, 6.5 [CI, 1.4-29.7]), and the use of residential septic systems was a risk for both Salmonella (OR, 3.2 [CI, 1.3-7.8]) and E. coli (OR, 5.7 [CI, 1.2-27.2]) O157 infection. CONCLUSIONS: Overall, non-food exposures were as important as food-related exposures with regard to their contributions to the proportion of cases. Infection prevention efforts should address kitchen hygiene practices and non-food exposures, such as recreational water exposure, in addition to food-consumption risks.

Seroprevalence of hepatitis B and C in juvenile detention entrants, Oregon, 1994-1996.

We tested sera originally collected from 1335 juvenile detention entrants for an HIV study in 1994-1996 for hepatitis B virus (HBV) and hepatitis C virus (HCV) antibodies; we found that the seroprevalence of HBV and HCV antibody was 2% and 1%, respectively. HBV was associated with Asian race, whereas HCV infection was associated with injection drug use and female gender.

Factors affecting surveillance data on Escherichia coli O157 infections collected from FoodNet sites, 1996-1999.

To determine the burden of illness caused by Escherichia coli O157 infections in populations in Foodborne Diseases Active Surveillance Network (FoodNet) surveillance areas, we initiated active, laboratory-based surveillance and surveyed laboratories, physicians, and the general public regarding the factors associated with the diagnosis and surveillance of infection with E. coli O157. We evaluated survey responses and site-specific incidence, outbreak, and demographic data during 1996-1999. A total of 1425 laboratory-confirmed cases of E. coli O157 infection and 32 outbreaks were reported from the 5 original FoodNet sites. The average annual incidence ranged from 0.5 cases/100,000 population in Georgia to 4.4 cases/100,000 population in Minnesota. After excluding outbreak-associated cases, the annual incidence of sporadic, laboratory-confirmed E. coli O157 infections remained relatively stable during 1996-1999, with a range of 1.9-2.3 cases/100,000 population. Regional differences in incidence partly resulted from differing physician and laboratory practices and from site-specific exposure factors (e.g., living on or visiting farms).

Outbreak of Pseudomonas aeruginosa infections caused by commercial piercing of upper ear cartilage.

CONTEXT: Sporadic infections following ear piercing are well documented, but common-source outbreaks are rarely recognized. OBJECTIVE: To investigate reports of auricular chondritis subsequent to commercial ear piercing. DESIGN, SETTING, AND SUBJECTS: Outbreak investigation by Oregon public health agencies, including cohort study of persons pierced at a jewelry kiosk in August-September 2000, environmental sampling, and molecular subtyping of isolates. Confirmed cases had Pseudomonas aeruginosa cultured from ear wounds. Suspected cases had signs and symptoms of external ear infection, including drainage of pus or blood for at least 14 days. MAIN OUTCOME MEASURES: Risk factors for infection and comparison of bacterial isolates by molecular subtyping. RESULTS: From 186 piercings in 118 individuals, we identified 7 confirmed P aeruginosa infections and 18 suspected infections. Confirmed cases were 10 to 19 years old. Most were initially treated with antibiotics ineffective against Pseudomonas. Four were hospitalized, 4 underwent incision and drainage surgeries (1 as an outpatient), and several were cosmetically deformed. Upper ear cartilage piercing was more likely to result in either confirmed or suspected infection than was lobe piercing (confirmed: RR undefined, P<.001; suspected: RR, 3.6; 95% confidence interval, 1.5-8.5). All persons with confirmed infections had their ear cartilage pierced with an open, spring-loaded piercing gun. Patient isolates were indistinguishable by molecular subtyping, and matching isolates were recovered from a disinfectant bottle and nearby sink. At least 1 worker admitted sometimes spraying the disinfectant on the ear studs before piercing. CONCLUSIONS: Ear cartilage piercing is inherently more risky than lobe piercing. Clinicians should respond aggressively to potential auricular chondritis and consider Pseudomonas a possible cause pending culture results.

Alfalfa seed decontamination in a Salmonella outbreak.

Based on in vitro data, the U.S. Food and Drug Administration recommends chemical disinfection of raw sprout seeds to reduce enteric pathogens contaminating the seed coats. However, little is known about the effectiveness of decontamination at preventing human disease. In 1999, an outbreak of Salmonella enterica serotype Mbandaka occurred in Oregon, Washington, Idaho, and California. Based on epidemiologic and pulsed-field gel electrophoresis evidence from 87 confirmed cases, the outbreak was linked to contaminated alfalfa seeds grown in California's Imperial Valley. Trace-back and trace-forward investigations identified a single lot of seeds used by five sprout growers during the outbreak period. Cases of salmonellosis were linked with two sprout growers who had not employed chemical disinfection; no cases were linked to three sprout growers who used disinfection. This natural experiment provides empiric evidence that chemical disinfection can reduce the human risk for disease posed by contaminated seed sprouts.

Verotoxigenic Escherichia coli Infection: U.S. Overview †.

Escherichia coli O157:H7 remains a public health problem in the United States despite a dramatic increase in the awareness of, and concern about, foodborne infections since the 1993 multistate E. coli O157:H7 epidemic. Although surveillance data can be difficult to interpret, the incidence of endemic disease caused by this organism is probably not increasing, and might be decreasing, at least in selected populations. With increased recognition of E. coli O157:H7 infection has come the investigation of increasing number of outbreaks, leading to the recognition of many "new" vehicles, including some foods not traditionally associated with enteric infections, such as dry-cured salami and lettuce. Molecular fingerprinting techniques are being used to track the transmission of E. coli O157:H7 through human populations. Analysis of DNA encoding virulence factors and surface antigens suggests that diarrheagenic E. coli have evolved by acquiring large DNA fragments, with subsequent chromosomal recombination. Some Shiga toxin-producing E. coli other than E. coli O157:H7 are no doubt pathogens, but the majority of these toxigenic strains found in food are probably not virulent. More research is needed to define the characteristics that render selected Shiga toxin-producing organisms harmful to humans.