Outbreak of escherichia coli O157: H7 infections after Petting Zoo visits, North Carolina State Fair, October-November 2004.

OBJECTIVES: To identify cases, describe the outbreak, implement control measures, and identify factors associated with infection or protection from infection, including contact with animals and hand hygiene practices. DESIGN: Case finding, a case-control study of 45 cases and 188 controls, environmental investigation, and molecular subtyping of clinical and environmental Escherichia coli O157:H7 isolates. SETTING: The 2004 North Carolina State Fair. PARTICIPANTS: Case patients were fair visitors who had laboratory-confirmed E coli O157 infections, hemolytic uremic syndrome (HUS) diagnoses, or bloody diarrheal illnesses. Control subjects were recruited from a randomized list of persons who had purchased fair tickets online. Environmental samples from the fairgrounds were obtained from locations that had held animals during the fair. Main Exposure Visiting a petting zoo. MAIN OUTCOME MEASURES: Case finding: Summary descriptive statistics of suspected, probable, or confirmed E coli O157:H7 infections, signs, symptoms, and HUS. Environmental investigation: E coli O157:H7 isolates, pulsed-field gel electrophoresis patterns, and spatial distribution of source locations. Case-control study: Odds ratios (ORs) comparing reported fair-related activities, hygiene practices, and zoonotic disease knowledge with outcome. RESULTS: A total of 108 case patients were ascertained, including 41 with laboratory-confirmed illness and 15 who experienced HUS. Forty-five case patients and 188 controls were enrolled in the case-control study. Visits to a petting zoo having substantial environmental E coli O157:H7 contamination were associated with illness (age-adjusted OR, 8.2; 95% confidence interval [CI], 3.3-20.3). Among children 5 years or younger who had visited the implicated petting zoo, contact with animal manure (OR, 6.9; 95% CI, 2.2-21.9) and hand-to-mouth behaviors (OR, 10.6; 95% CI, 2.0-55.0) were associated with illness. Reported hand hygiene practices did not differ significantly (OR, 1.8; 95% CI, 0.3-9.5). Reported awareness of the risk for zoonotic disease was protective (OR, 0.1; 95% CI, 0.03-0.5). Environmental samples from the petting zoo implicated in the case-control study yielded E coli O157:H7, with indistinguishable pulsed-field gel electrophoresis patterns from the predominant strain. CONCLUSIONS: We describe one of the largest petting zoo outbreaks of E coli O157:H7 to date. Persons became infected after contact with manure and engaging in hand-to-mouth behaviors in a petting zoo having substantial E coli O157:H7 contamination. Use of alcohol-based hand-sanitizing gels was not protective, although knowledge of the risk for zoonotic infection was protective. Future investigations in similar outbreaks should assess risks for infection and protective measures (eg, physical barriers separating visitors from animal manure, education, and appropriate hand hygiene practices).

Using Influenza-Like Illness Data to Reconstruct an Influenza Outbreak.

The objective of this study was to reconstruct the type A influenza epidemic that occurred in the Research Triangle Park (RTP) region of North Carolina during the 2003-04 flu season. We describe an agent-based influenza transmission model that uses Influenza-like Illness (ILI) data gathered from state agencies to estimate model parameters. The design of the model is similar to models represented in the literature that have been used to predict the impact of pandemic avian influenza in Southeast Asia and in the continental United States and to assess containment strategies. The focus of this model aims to reconstruct a historical epidemic that left traces of its impact in the form of an ILI epidemic curve. In this context, the work assumes aspects of a curve fitting exercise.

Cyclical changes in seroprevalence of leptospirosis in California sea lions: endemic and epidemic disease in one host species?

BACKGROUND: Leptospirosis is a zoonotic disease infecting a broad range of mammalian hosts, and is re-emerging globally. California sea lions (Zalophus californianus) have experienced recurrent outbreaks of leptospirosis since 1970, but it is unknown whether the pathogen persists in the sea lion population or is introduced repeatedly from external reservoirs. METHODS: We analyzed serum samples collected over an 11-year period from 1344 California sea lions that stranded alive on the California coast, using the microscopic agglutination test (MAT) for antibodies to Leptospira interrogans serovar Pomona. We evaluated seroprevalence among yearlings as a measure of incidence in the population, and characterized antibody persistence times based on temporal changes in the distribution of titer scores. We conducted multinomial logistic regression to determine individual risk factors for seropositivity with high and low titers. RESULTS: The serosurvey revealed cyclical patterns in seroprevalence to L. interrogans serovar Pomona, with 4-5 year periodicity and peak seroprevalence above 50%. Seroprevalence in yearling sea lions was an accurate index of exposure among all age classses, and indicated on-going exposure to leptospires in non-outbreak years. Analysis of titer decay rates showed that some individuals probably maintain high titers for more than a year following exposure. CONCLUSION: This study presents results of an unprecedented long-term serosurveillance program in marine mammals. Our results suggest that leptospirosis is endemic in California sea lions, but also causes periodic epidemics of acute disease. The findings call into question the classical dichotomy between maintenance hosts of leptospirosis, which experience chronic but largely asymptomatic infections, and accidental hosts, which suffer acute illness or death as a result of disease spillover from reservoir species.

Use of a case-control study and geographic information systems to determine environmental and demographic risk factors for canine leptospirosis.

Leptospirosis is increasingly diagnosed as a re-emerging canine disease in the USA. Our objectives were to describe potential risk factors for canine leptospirosis infections in northern California, through the use of a case-control study, and to perform a spatial analysis to investigate which aspects of the landscape and land use patterns are important in the transmission of leptospirosis. Forty-three cases and 59 controls were enrolled into the study. Serological results showed that 17 (39.5%) of the 43 dog cases were infected with serovar pomona. Cases were 7.86 times more likely to have been walked in a rural environment rather than an urban environment. Cases also had eight times higher odds of swimming in outdoor water, and approximately 12 times higher odds of drinking from outdoor water in the two weeks preceding illness. At smaller distances from the dogs' homes (radius or= 5 km) there was a positive relationship between leptospirosis cases and percent of wetlands or public open space. Intervention measures for the prevention of canine leptospirosis should include reducing access to potentially infectious bodies of water that are close to canine homes, and to large areas of wetlands and public open space in the general vicinity. We have shown that a spatial analysis in conjunction with traditional epidemiological analysis is a powerful combination in identifying risk factors for infectious diseases.

Defining and applying a method for improving the sensitivity and specificity of an emergency department early event detection system.

The sensitivity and specificity of syndrome definitions used in early event detection (EED) systems affect the usefulness of the system for end-users. The ability to calculate these values aids system designers in the refinement of syndrome definitions to better meet public health needs. Utilizing a stratified sampling method and expert review to create a gold standard dataset for the calculation of sensitivity and specificity, we describe how varying syndrome structure impacts these statistical parameters and discuss the relevance of this to outbreak detection and investigation.

State plans for containment of pandemic influenza.

This review assesses differences and similarities of the states in planning for pandemic influenza. We reviewed the recently posted plans of 49 states for vaccination, early epidemic surveillance and detection, and intraepidemic plans for containment of pandemic influenza. All states generally follow vaccination priorities set by the Advisory Committee on Immunization Practices. They all also depend on National Sentinel Physician Surveillance and other passive surveillance systems to alert them to incipient epidemic influenza, but these systems may not detect local epidemics until they are well established. Because of a lack of epidemiologic data, few states explicitly discuss implementing nonpharmaceutical community interventions: voluntary self-isolation (17 states [35%]), school or other institutional closing (18 [37%]), institutional or household quarantine (15 [31%]), or contact vaccination or chemoprophylaxis (12 [25%]). This review indicates the need for central planning for pandemic influenza and for epidemiologic studies regarding containment strategies in the community.