In late October 2004, the North Carolina Division of Public Health (NCDPH) received several reports of hemolytic uremic syndrome (HUS) among North Carolina residents who had attended the State Fair, which ran from October 14 to 24 in Raleigh, North Carolina. Since attendance at the fair typically averages 800,000 visitors annually, the NCDPH recognized the potential for a large outbreak and immediately alerted local health departments, asking them to increase surveillance for diarrheal illnesses. On November 1, the NCDPH requested epidemiologic support from the Centers for Disease Control and Prevention (CDC).
Initially, all patients who reported diarrheal illness were interviewed by local and state health department staff using the CDC’s Standard Foodborne Disease Outbreak Case Questionnaire. As the number of ill individuals rose, however, investigators used an abbreviated version of the questionnaire available on-line through the state’s public health website. Descriptive analysis of early case reports noted the relevance of fair and petting zoo attendance. Health officials soon refined their investigation further and began a case-control study.
In this study, a case was defined as a person with: a) laboratory confirmed E. coli O157:H7, b) a clinical diagnosis of HUS or Thrombotic Thrombocytopenic Purpura (TTP) diagnosed after October 15, 2004, or c) bloody diarrhea in a person who developed diarrhea after October 15 and who had attended the North Carolina State Fair between October 15 and November 7, 2004. A control was defined as a person who attended the State Fair between October 15 and 24 and did not develop diarrhea through November 11. Controls were selected randomly from a list of persons who had purchased tickets for the fair online, at kiosks, or in malls. Cases and controls were asked about ten areas where human contact with animals could have occurred, hand-washing practices at the fairgrounds, foods and beverages consumed, and other activities at the fair.
As required by North Carolina reportable disease laws, clinical laboratories submitted E. coli O157:H7 isolates to the state Laboratory for Public Health (LPH) for confirmation, toxin assay, and pulsed field gel electrophoresis (PFGE) molecular subtyping. PFGE enzyme patterns were uploaded to PulseNet, the National Molecular Subtyping Surveillance System for foodborne diseases, which is maintained by scientists at the CDC.
Investigators visited the state fairgrounds on several occasions and consulted with North Carolina Department of Agriculture and Consumer Services (NCDACS) fair officials regarding specific activities that might have factored in the outbreak. They obtained information about animals exhibited at the fair, areas where persons could have had direct contact with animals, and the layout of animals and pens in each of the animal areas. Livestock exhibits including goats, sheep, pigs, and cattle presented the greatest opportunity for fairgoers to have contact with animals. Animals were exhibited at 10 sites, including two commercial petting zoos, Commerford and Sons Petting Zoo and Crossroads Farm Petting Zoo.
Commerford and Sons Petting Zoo housed animals in pens. Visitors could reach over or through railings to touch the animals in this exhibit. Crossroads Farm Petting Zoo allowed persons to walk among and have extensive direct contact with sheep and goats. Both petting zoos allowed feeding. Hand sanitizer was available at both petting zoos. Neither erected handwashing facilities at or near the exhibit, though handwashing facilities certainly existed elsewhere on the fairgrounds.
Investigators collected composite ground samples and surface swab samples from structures from ten separate areas where animals were present, as well as two other areas of interest. After the fair had ended, a variety of other environmental samples were obtained from both animal and non-animal areas.
Inspection records at all food and beverage vendors were reviewed; consumer complaints were investigated. Information on cleaning methods and composition of cleaning agents used for cleaning facilities and hand sanitizer used in dispensers during the fair were also compiled and examined.
Results of the outbreak investigation are reported in a document, “Outbreak of Shiga toxin producing E. coli (STEC) infection associated with a petting zoo at the North Carolina State Fair – Raleigh, North Carolina, November 2004,” dated June 29, 2005. In total, 108 cases of diarrheal illness were attributed to the outbreak. Of these, forty-one were laboratory confirmed with E. coli O157:H7, six were classified as probable cases, and 59 were classified as suspect cases. There were eighteen secondary cases. Fifty percent of the cases were under six years old. Ninety-three percent reported attending the fair and 89% reported petting zoo contact.
Thirty eight of the forty-one E. coli O157:H7 isolates obtained from cases shared an indistinguishable PFGE XbaI and BlnI pattern; these were designated Pattern A. The three remaining isolates demonstrated unique PFGE patterns and were classified as Patterns G, H, and J.
Eighteen of 96 environmental samples collected at the fairgrounds on November 3 were positive for E. coli O157:H7. Ten of fifteen samples obtained at the Crossroads Petting Zoo site were also positive. On November 9, investigators collected more samples at the Crossroads exhibit in areas where people could have direct contact with sheep and goats. Nineteen of these thirty samples were culture positive for E. coli O157:H7. All nineteen had PFGE patterns indistinguishable from Pattern A. Eight specimens collected at sites other than the Crossroads Petting Zoo exhibit also tested positive for E. coli O157:H7; five of the eight matched each other but not Pattern A, the pattern seen in thirty-eight of forty-one laboratory confirmed cases, as well as in samples taken from the Crossroads Petting Zoo site.
Investigators concluded that the case-control study, laboratory investigation, and environmental sampling consistently associated most outbreak illnesses with exposures at Crossroads Farm Petting Zoo. They attributed the exposures to three factors: 1) animals shedding E. coli O157:H7, 2) intensive and extensive contact with animals, and 3) behaviors associated with very young ages. Investigators further hypothesized that the high number of animals in the Crossroads Farm Petting Zoo area likely increased animal stress level, and some animals were noted by the owner of the Crossroads Farm Petting Zoo to have had loose stools.
The final report ends with recommendations to prevent similar outbreaks from happening in the future. These include prohibiting or discouraging direct contact with farm animals, particularly among vulnerable populations such as the very young or those with compromised immune systems, providing direct supervision at the exhibits so that contaminated bedding can be removed promptly, and having proper hand-washing facilities for use by petting zoo visitors.
While some diseases show host species specificity, meaning that they can only occur in one animal species, many other diseases can be spread between different animal species, including humans and animals. These diseases are collectively known as zoonotic diseases. The term zoonoses, is derived from Greek zoon (animals) and noses (diseases) that literally mean diseases from animals.
Zoonotic diseases can be transmitted by a variety of routes. Some documented ways include direct and indirect contact with infected animals, airborne exposure to infective agents shed by animals, consumption of animal products, consumption of water that has been contaminated by animal fecal material, or exposure to insect vectors such as fleas or ticks.
Previously, the primary mode of transmission of zoonotic diseases at agricultural fairs, petting zoos, and farm visits was thought to be fecal-oral, that is, by ingestion of bacteria-laden feces via contaminated food or water, or transfer by hand to mouth following contact with contaminated surfaces or animals. Conclusions reached by investigators in several recent fair-associated outbreaks of E. coli O157:H7 suggest that ingestion or perhaps even inhalation of contaminated dust particles may also be how fair attendees become infected with the bacteria.
Summaries of Known Cases of Zoonotic Pathogen Outbreaks Associated with State and County Fairs, Petting Zoos, and Community Activities Involving Human-Animal Contact
Outbreak Case 1: County Fair – Wisconsin
MMWR Weekly (November, 1988) reported that in September, 1988, a human was fatally infected with swine influenza virus in Wisconsin. A subsequent investigation found that the victim, a woman, had attended a county fair and visited the display area of the pig barn. Statements from the veterinarians at the fair indicated that pigs in the display area were found to show an illness consistent with swine influenza. A preliminary investigation found that there was no outbreak of influenza-like illness observed in the surrounding areas. Three healthcare personnel treating the case patient also developed influenza-like illness with laboratory evidence of Swine Influenza Virus (SIV) infection (Wells et al., 1991). The editorial note contained in the MMWR Weekly report indicated that the case suggested direct transmission of influenza virus from pig to human host.
Outbreak Case 2: Farm Visitor Center – Leicestershire, United Kingdom
Shukla et al (1995) investigated an outbreak of seven cases of E. coli O157:H7 infection associated with a visit to a farm in Leicestershire, United Kingdom, during the summer of 1994. A joint study was conducted between environmental health officers and the local veterinary investigation center of the Ministry of Agriculture, Fisheries and Food. A questionnaire was sent to all cases. Samples were collected from the farm, and the associated facilities for food preparation and hygiene were also assessed. The investigation found that the common factor linking all the cases was a visit to a farm visitor center in the three weeks before the onset of the illnesses. The epidemiological data supported this link, as the strains of E. coli O157:H7 isolated from nine animals on the farm were indistinguishable from those isolated from the human samples. This report concluded that the most likely cause of this outbreak was direct human contact with animals. The probability of contracting disease was increased by poor hand washing facilities, and a lack of information provided to the visitors on the importance of maintaining personal hygiene.
Outbreak Case 3: Farm Visit – Wales
In April 1995, an outbreak of Cryptosporidiosis was reported among 43 children and four staff after visiting a rural farm (Evans and Gardner, 1996). Out of the 43 cases reported, 7 were confirmed by laboratory cultures. The investigation indicated that the highest likelihood of source of contamination was contact with calves.
Outbreak Case 4: Farm Visit – Dublin
Sayers et al (1996) reported a Cryptosporidium outbreak the summer of 1995, involving 13 children identified as cases. The children had been to a summer project and visited an open farm in Dublin, Ireland. The second part of this study also included a case control study of 52 out 55 people who had visited the open farm.
The researchers concluded that the outbreak was significantly associated with playing in the sand on a picnic area beside the stream where animals had access. This outbreak emphasizes the risk associated with children visiting open farms.
Outbreak Case 5: Farms – Cornwall and West Devon, United Kingdom
Milne et al (1999) investigated an E. coli O157:H7 outbreak associated with a farm in the United Kingdom during the period of June to July, 1997. A Vero cytotoxins producing Escherichia coli O157:H7 infection was observed in three children, one who lived on an open farm and two who visited the farm during school parties. Two of the three children developed HUS and one suffered from severe neurological impairment. Isolates collected from the three children and from all environmental samples were indistinguishable by molecular typing, providing evidence of the link between the human contact with the farm and the outbreak.
The farm was closed voluntarily for six weeks, while recommendations to reduce the risk of transmission were implemented. These recommendations included reassessing provisions made for general hygiene, including making sure adequate hand washing facilities were available; strict segregation of eating and drinking areas from the animal contact area; reinforcement of precautions to be taken by visitors; reassessment of the species type and age of animals kept in the touching barn; prohibition of visitor exposure to fecal contamination (e.g. manure heaps, etc.); elimination of visitor use of cattle trails unless devoid of fecal contamination; implementing a “no touch” policy in various parts of the farm trail, like the calf pen area; enhancing decontamination of the goat paddock by putting it out of use a few weeks before the visits and keeping the grass short; performing rigorous detergent cleaning in areas of public access and appropriate use of disinfectants; and prohibiting public asses to the milking parlors, and calving barns.
Outbreak Case 6: Zoo Water Fountain – Minnesota
In July 1997, the Minnesota Department of Health (MDH) reported an outbreak of Cryptosporidiosis among children who visited the Minnesota Zoo (MMWR Weekly, October, 1998). A total of 369 cases were reported, of which 73 were subsequently confirmed by means of laboratory cultures. The report by MDH indicated case onset of vomiting or diarrhea 3 to 15 days after exposure to the zoo fountain. However, the fountain was not confirmed as the source. Exclusion of people from the suspect water fountain was suggested to reduce the risk of contamination to the public.
Outbreak Case 7: Agricultural Fair – British Columbia
During August and September of 1998 the British Columbia Center for Disease Control sent all E. coli O157:H7 isolates to an outside laboratory for molecular sub-typing (BC Center for Disease Control, March, 1999). On September 17 it was reported that nine of the 69 referred isolates had a common genotype. Three individuals were hospitalized, though none developed hemolytic-uremic syndrome (HUS). Seven of the nine had onset of illness within ten days of visiting a large agricultural fair. Despite in-depth interviews, no common source of infection could be identified. No environmental investigation of the fair could be carried out; because by the time laboratory results were available the fair had closed.
Outbreak Case 8: County Fair – Puyallup, Washington
An outbreak of hemorrhagic colitis due to E. coli O157:H7 was identified among visitors to the Puyallup Fair in Puyallup, Washington, during September of 1998 (CDC Memorandum, March 1999). Two children were initially confirmed as being ill from E. coli O157:H7. The Communicable Disease State Epidemiologist at the Washington State Department of Health mentioned in a news release immediately after the detection of two confirmed cases at the Puyallup fair that health officials were looking for food borne exposure as well as possible contamination at the animal petting areas and on water rides (Kobayashi, 1998).
The CDC conducted an investigation, and concluded that out of 80 ill people reporting, there were three confirmed and five probable cases of E. coli O157:H7 illness. Of these eight cases, seven reported consuming hamburgers, though purchased from multiple vendors. The environmental investigation suggested that exposure could have resulted from consuming food without washing hands after petting the animals in the petting zoo. The internal temperature of the cooked hamburgers tested ranged between 155 to 195? F although a number of situations of potential cross contamination were observed among the food handlers.
The CDC memorandum stated that compelling circumstantial, but not conclusive, evidence was found that the outbreak was a result of consumption of contaminated hamburgers. The memorandum also recommended enforcing proper food handling practices among food vendors, installing a large number of hand washing facilities at the animal petting zoo, and also throughout the fair. It also recommended performing a hazard evaluation of all the food sold at the fair for potential risk of foodborne illnesses.
Outbreak Case 9: Farm – North Wales, London
Payne et al (2003) reported an outbreak of Vero toxin producing E. coli O157:H7 (VTEC O157:H7) causing gastroenteritis among people visiting an open farm in North Wales, London in June 1999. A case-control study was designed which included 16 primary case patients and 36 controls. The preliminary investigation indicated a significant association between attendance on the second day of the festival, eating ice cream or cotton candy and contact with cows or goats. Further multivariable analysis of the data indicated that the only the association of the illness with eating ice cream and cotton candy remained significant. The researchers suggested that foods on open farms should be eaten only in the dedicated clean areas, and sticky food should be avoided in such events.
Outbreak Case 10: County Fair – Washington County, New York
The New York State Department of Health investigated what is believed to be the largest outbreak of waterborne E. coli O157:H7 illness in United States history. The outbreak occurred at a fair in Washington County, New York, in August of 1999 (New York State Department of Health, March, 2000). A total of 781 persons were identified with suspected infections of E. coli O157:H7 and/or Campylobacter jejuni. Of these cases 127 persons were culture confirmed to be ill with E. coli O157:H7, 71 individuals were hospitalized, 14 persons exhibited hemolytic uremic syndrome (HUS), and 2 people died. A household telephone survey indicated that the number of people infected by either pathogen after visiting the Washington County Fair might be as high as 2,800. The environmental and site investigation indicated that unchlorinated water from a well serving the southwestern portion of the fairgrounds was contaminated with E. coli O157:H7 (DOH News, 1999). Samples of manure collected from a barn located 50 feet from the well and samples from the groundwater flow from the manure storage area located 80 feet from the well tested negative for E. coli O157:H7. However, samples from the septic system tested positive for E. coli O157:H7.
The shape of the epidemic curve suggested a point source outbreak with the peak of symptom onset occurring on September 1. Considering a typical incubation period of 2-4 days, this suggested that most exposures took place towards the end of the fair. This matched information provided by the patients, 88% of whom visited the fair in the final week. Consumption of only two food or beverage items, soda with ice or ice in any drink, was reported by a majority of the culture-confirmed case patients. MMWR Weekly (1999) reported that the pulsed-field gel electrophoresis testing by the Wadsworth center indicated that the DNA fingerprints of E. coli O157:H7 isolates from the well, the water distribution system, and most confirmed cases were similar.
The epidemiological investigation of this outbreak concluded that a significant relationship was associated with the incidence of the outbreak and the consumption of beverages purchased from vendors supplied with water from the unchlorinated well. MMWR Weekly (1999) reported that letters were sent to nursing homes, hospitals and schools to exclude the symptomatic personnel and also follow careful hygienic practices to prevent secondary transmission.
Outbreak Case 11: Agricultural Fair – Ontario, Canada
Warshawsky et al (2002) investigated an outbreak of E. coli O157:H7 associated with a large agricultural fair conducted between September 10 and 19, 1999, in Ontario, Canada. This study indicated that 7 cases of E. coli O157:H7 infections were associated with animal contact at the agricultural pavilion of the regional fair. Sub-typing revealed that five of the seven cases were extremely uncommon E. coli O157:H7 PT 27 while the remaining two were common E. coli O157:H7 PT 14. The E. coli O157:H7 PT 27 pattern matched with three samples from goats and one sample from sheep from the traveling petting zoo. The researchers further noted that the clustering of positive cases on the two weekends of the fair indicated that exposures could be a result of difficulty in manure disposal and environmental cleaning due to high volumes of visitors. The results from this case control study strongly suggested that the goats and sheep from the petting zoo were the source of the E. coli O157:H7. The detailed history from two primary sources indicated that the rails and the environment surrounding the petting zoo could also have been contaminated and could have acted as a source of transmission. The researchers recommended that standards should be outlined for adequate hand washing facilities, appropriate disposal of manure, proper cleaning environment surrounding the petting zoos, including the rails and floors.
Outbreak Case 12: Social Event in Cow Pasture – Petersburg, Illinois
An outbreak of E. coli bacteria was reported in Petersburg, Illinois inn 1999 (Nando Times, 1999). The outbreak took place among 1,800 people who attended a party called “Cornstalk” held in a cow pasture. State health officials reported that 202 individuals became ill, and that 20 were hospitalized. However, none of the reported illnesses were considered serious. The source of contamination was not found.
Outbreak Case 13: Petting Zoo – Snohomish County, Washington
A press release by the Snohomish Health District, Communicable Disease Control (June, 2000) reported five cases of bacterial diarrhea caused by E. coli O157:H7 in children in Snohomish County in May 2000. Three of the children visited a petting zoo several days before they became sick. The fourth child did not visit the petting zoo, but was found to live on another farm where cattle were raised (MMWR Weekly, April 2001) reported an investigation of the farm by Snohomish Health District (SHD) and Washington Department of Health revealed that the children were allowed to touch young poultry, rabbits and goats. Children brought their own lunches and ate approximately 50 feet from the penned animals. The study also indicated that the animal stool samples collected from the farm tested negative for E. coli O157:H7. The Health District believed that the three children visiting the petting zoo acquired the bacterial diarrhea due to a lack of adequate hand washing facilities available. MMWR weekly (April 2001) also reported that no signs were posted to instruct the visitors to wash their hands after touching the animals.
Outbreak Case 14: County Fair – Medina County, Ohio
Crump et al (2000) discussed county fairs as risk factors for E. coli O157:H7 infections. The researchers investigated a cluster of E. coli O157:H7 isolates observed in Medina County, Ohio, in August of 2000. In this case control study 43 culture confirmed E. coli O157:H7 cases were identified. The environmental investigation suggested that contamination of a section of the water distribution system supplying various vendors was most consistent with the localization of the pathogenic exposure. Water samples collected for this study did not indicate any coliforms. However, a Halloween event was arranged on the same fairgrounds where the Medina County Fair was held, during which five children developed E. coli O157:H7 infection. These children consumed water-based products during the party and showed the same PFGE pattern as that observed in the Medina County Fair outbreak. The researchers concluded that the county fair exposure was significantly associated with the E. coli O157:H7 outbreaks. The report recommended that guidelines be developed for safer interactions between animals, humans, and the environment. These recommendations could include improving public awareness of risk and prevention strategies, identifying high-risk animals, and controlling their contact with humans through identifying interaction activities and groups at greater risk.
Outbreak Case 15: Dairy Farm – Pennsylvania
Crump et al (2002) discussed an outbreak of E. coli O157:H7 among visitors to a dairy farm in Pennsylvania in September, 2000. A case control study among the visitors was conducted to identify the risk factors of infection, along with a household survey to determine the rates of diarrheal illness. The total number of confirmed or suspected E. coli O157:H7 cases were determined to be fifty-one. The median age among the patients was four. Eight of the cases developed hemolytic uremic syndrome (HUS). The environmental investigation indicated that 28 of 216 cattle (13%) on the farm were carrying E. coli O157:H7 that yielded an identical pattern when analyzed by pulsed field gel electrophoresis to that observed for the isolates of the patients. The organism was also recovered from various surfaces in public access areas of the farm.
MMWR Weekly (April 2001) reported that a case control study among the farm visitors was conducted jointly by the CDC, Pennsylvania Department of Health, and Montgomery County Health Department to identify the risk factors. A “confirmed case” was defined as diarrhea in a person within 10 days of visiting the farm on or after September 1, with either E. coli O157 isolated from stool or HUS. A “probable case” was defined as diarrhea in a person within 10 days of visiting the farm on or after September 1. A “control” was defined as a person visiting the farm after September 1 who did not develop diarrhea within 10 days of the visit. Fifty-one case patients and ninety two controls were interviewed for this case control study. The research concluded that this large outbreak of E. coli O157:H7 was most likely a result of contamination of both animal hides and the environment. This study also reported that the data showed hand washing as providing protection against transmission of the pathogen.
Outbreak 16: Petting Zoo – Worcester, Pennsylvania
An article published by WebMD Medical News on April 23, 2001 (Bloomquist, 2001), reported an outbreak of E. coli O157:H7 among visitors to the Merrymead Farm petting zoo in Worcester, Pennsylvania. In all, 16 children who had visited the zoo contracted E .coli, and it was suspected that another 45 people became ill from the bacteria. The report indicated that one week after visiting the zoo, one of the children came down with violent stomach cramps and was hospitalized. A few days later, and after being released from the hospital, the patient was diagnosed with kidney failure. It is believed that 26 cows on the farm were carrying the E. coli bacteria, and that exposure may have occurred as visitors rode in a wagon which was caked with mud and animal manure, or as they touched animals that may have been infected.
Outbreak 17: County Fair – Ozaukee County, Wisconsin
The Ozaukee County Public Health Department and Wisconsin Department of Health and Family Services (2001) investigated an outbreak of E. coli O157:H7 associated with animals at the Ozaukee County Fair in August, 2001. A total of 59 E. coli O157:H7 cases were identified in this outbreak, with 25 laboratory confirmed cases (25 “primary cases” and 34 probable cases). Bacteriological testing of water at the Ozaukee County fairgrounds and the Fireman’s park did not indicate presence of E. coli O157:H7, though 10 of the 36 samples collected from the Ozaukee County Property showed elevated levels of total coliforms. The environmental investigation focused primarily on testing water samples from the livestock buildings, livestock washing stations, runoffs from settling basin, grass filter strip, manure storage area, fishing pond, and streams. A total of 19 surface water samples, and 8 sediment samples, were collected from the pond and stream on the fairgrounds property. All tested negative for E. coli O157:H7. Public health officials attributed the outbreak to animal contact in the petting zoo at the county fair (Cole et al, 2001).
As a consequence of this outbreak, the Wisconsin Division of Public Health, Wisconsin Department of Agriculture, Trade and Consumer Protection, and the Dane County Division of Public Health developed a list of voluntary guidelines for animal exhibitions at Wisconsin. The general precautions for livestock on public displays included providing hand-washing stations at strategic places around livestock barns, and posting signs encouraging their use. Actions included developing and implementing manure collection, handling, and storage procedures. It was recommended that runoffs into places where water was pulled be avoided. A written policy should be developed on handling animal bites and should be discussed with the corresponding county fair health authorities. Visitors should be prohibited from being in contact with baby animals, including newborns, if an animal birthing display is available. The recommendations regarding the food and hygiene practices included keeping food and beverage service away from the livestock, providing adequate hand washing facilities, and encouraging their usage. The guidelines also recommended keeping of records of all the vendors, vendor locations, and schedule of events.
Outbreak Case 18: County Fair – Lorain County, Ohio
The Department of Health and Human Services, Public Health Services (CDC memorandum, February, 2002) reported that 23 cases of E. coli O157:H7 infection were identified associated with the attendance at the Lorain County Fair, Ohio, in September, 2001. A number of additional cases of diarrhea were identified as likely due to secondary transmission from primary cases. The memorandum strongly associated presence at the Cow Palace, Lorain County, with bacterial diarrhea. The environmental and site investigation indicated that visible manure was present on the ground in at least one area of the barn floor. Out of 54 environmental samples, 23 tested positive for Shiga toxin producing E. coli O157:H7. Samples from the doorways, rails, bleachers, and sawdust exhibited an identical fingerprint pattern when analyzed by PFGE. Environmental samples of water obtained by the Health Department in the week before and during the fair tested positive for total coliforms for two spigots.
The CDC memorandum clearly associated the Lorain County Fair with the E. coli O157:H7 outbreak in the county. The possible mechanisms proposed for disease transmission included contamination of human hands with residual cow manure and/or aerosolized dispersion of E. coli O157:H7 in the sawdust. The memorandum also hypothesized that the patients became contaminated at the cow palace and were subsequently infected while eating or drinking at the various vendors. The case control study of this memorandum did not support an alternative hypothesis, that the fairground water was related with the outbreak. This investigation strongly supported the previous incidences of E. coli O157:H7 outbreaks associated with the county fair attendance. This memorandum also stressed the need for collaborative efforts between various public agencies to develop clear guidelines for ensuring the disinfection of the temporary facilities housing the animals. The recommendations provided in this memorandum included considering the banning of large dusty events, and the development of guidelines for disinfecting surfaces in the Cow Palace prior to events or to replace sawdust with non particulate ground covering. They also suggested that the fairgrounds should be provided with adequate hand washing facilities with hand sanitizers. Measures should be provided to prevent intermixing of water.
Outbreak Case 19: County Fair – Wyandot County, Ohio
The Ohio Wyandot County Health Department received a report of an E. coli O157 outbreak in September, 2001 (CDC memorandum, February, 2002). A total of 92 cases were identified, including 27 laboratory-confirmed E. coli O157 infections. Two cases were diagnosed with hemolytic uremic syndrome. Eighty-eight cases reported attending Wyandot County Fair before becoming ill. The source of the outbreak was not fully identified; however, the most likely source was believed to be contact with infected cattle. Disinfecting areas that house cattle, removal of fecal contamination from contact surfaces, and exclusion of calves or cows from petting areas were recommended. Active surveillance at the fairgrounds during the local fair or at large gatherings, along with strengthening measures to prevent water contamination, was suggested.
Outbreak Case 20: Farm – Wellington, New Zealand
An outbreak of Cryptosporidiosis was linked to a two-day farm educational event in the Wellington region of New Zealand. The total number of cases is unknown, but 23 cases were laboratory-confirmed. The most likely route of infection was determined to be from an infected animal. The outbreak was discussed in a report released in 2001 (Stefanogiannis et al, 2001).
Outbreak Case 21: County Fair – Lane County, Oregon
A news release from the Oregon Department of Human Services (Oregon, 2002) reported on hemorrhagic colitis from the Lane County Fair held during August, 2002, in Oregon. The report indicated that 56 primary and 14 presumptive secondary cases were identified. This is believed to be the largest E. coli O157:H7 outbreak in Oregon history. Two-thirds (66%) of the confirmed cases were <6 years old, and 56 % were <19 years old.
Although not confirmed, health officials postulated that possible exposures leading to the outbreak occurred at animal enclosures, including the cattle tent, horse barn, and exposition halls that housed goats, sheep, rabbits, chickens, ducks, and guinea pigs. Investigators tried to trace the transmission path of the bacteria to develop a strategy to prevent the outbreak in the future. Capital Press, an agricultural magazine, discussed this event (September, 2002). The article mentioned that scientists discovered a virulent strain of bacteria on the pipes 15 feet above the goat pens in a fair exhibition hall, where about 75 people, including 12 children, were believed to be infected. A state epidemiologist from the Oregon Department of Human Services suggested that the microorganisms must have been present in the dirt and dust, and henceforth accumulated on the tops of the pipes 15 feet in the air.
Outbreak Case 22: Petting Zoo – Zutphen, The Netherlands
Heuvelink, et al (2002) reported that a young child developed a Shiga toxin 2 producing strain of Escherichia coli (STEC) O157 infection after visiting a petting zoo in Zutphen, The Netherlands. The STEC strains were isolated from the fecal samples from goats and sheep on the farm. Molecular sub-typing proved that the human and animal isolates were identical.
Outbreak Case 23: County Fair – Fort Bend County, Texas
In 2003 twenty-five people – fair visitors and animal exhibitors – became ill with E. coli O157:H7 after attending the Fort Bend County Fair in Rosenberg, Texas. There were four cases of Hemolytic Uremic Syndrome and one case of Thrombotic Thrombocytopenic Purpura. All seven laboratory-confirmed cases had an indistinguishable PFGE pattern which matched with ten isolates obtained from environmental samples taken at four animal husbandry sites. Case-patients ranged in age from 18 months to 67 years. Eighteen other environmental specimens were positive for E. coli O157:H7 but were determined by PFGE analyses to be different strains from the outbreak strain. Investigators concluded that both the rodeo and animal exhibit areas were heavily contaminated with E. coli O157:H7. There was no association between illness and food or beverage consumption (Reynolds et al, 2004; Durso et al, 2005).