A simulation model for assessing aberration detection methods used in public health surveillance for systems with limited baselines.

Public health officials continue to develop and implement new types of ongoing surveillance systems in an attempt to detect aberrations in surveillance data as early as possible. In public health surveillance, aberrations are traditionally defined as an observed value being greater than an expected historical value for that same time period. To account for seasonality, traditional aberration detection methods use three or more years of baseline data across the same time period to calculate the expected historical value. Due to the recent implementation of short-term bioterrorism surveillance systems, many of the new surveillance systems have limited historical data from which to calculate an expected baseline value. Three limited baseline aberration detection methods, C1-MILD, C2-MEDIUM, and C3-ULTRA, were developed based on a one-sided positive CUSUM (cumulative sum) calculation, a commonly used quality control method used in the manufacturing industry. To evaluate the strengths and weakness of these methods, data were simulated to represent syndromic data collected through the recently developed hospital-based enhanced syndromic surveillance systems. The three methods were applied to the simulated data and estimates of sensitivity, specificity, and false-positive rates for the three methods were obtained. For the six syndromes, sensitivity for the C1-MILD, C2-MEDIUM, and C3-ULTRA models averaged 48.2, 51.3, and 53.7 per cent, respectively. Similarly, the specificities averaged 97.7, 97.8, and 96.1 per cent, respectively. The average false-positive rates for the three models were 31.8, 29.2, and 41.5 per cent, respectively. The results highlight the value and importance of developing and testing new aberration detection methods for public health surveillance data with limited baseline information.

Characteristics of meta-analyses related to acceptance for publication in a medical journal.

Editors of medical journals select manuscripts for publication based, in part, on the perceived quality of the manuscript submitted. The objective of this study was to describe associations between acceptance for publication and quality-related methodologic characteristics of meta-analyses. This was a prospective observational study. The setting was editorial offices of JAMA and offices of external reviewers. The manuscripts reviewed were 112 consecutive meta-analyses submitted to JAMA during 1996 and 1997 whose authors agreed to participate. The main outcome measures were ratings of 16 methodologic characteristics reflecting quality of the meta-analysis and acceptance for publication. A "high" rating for one methodologic characteristic, whether the report of the meta-analysis provided sufficient detail to enable replication, was related significantly to publication (RR = 2.79, 95% CI = 1.13-6.89). This relationship persisted when other variables were controlled for in the model. Generally, rejected manuscripts had fewer factors rated "high," but differences were not significant. We found that inclusion of sufficient detail to allow a reader to replicate meta-analytic methods was the only characteristic related to acceptance for publication.

Multiple risk factors and population attributable risk for ischemic heart disease mortality in the United States, 1971-1992.

The objective of this study was to assess the associations and population attributable risks (PAR) of risk factor combinations and ischemic heart disease (IHD) mortality in the United States. We used logistic regression models to assess the association of risk factors with IHD in the First National Health and Nutrition Examination Survey (1971-1974) and Epidemiologic Follow-up Study (1982-1992) among white and black men and women. We examined eight modifiable risk factors: hypertension, elevated serum cholesterol, diabetes, overweight, current smoking, physical inactivity, depression, and nonuse of replacement hormones. Risk factors associated with IHD mortality were the same among white and black men (i.e., age, education, smoking, diabetes, hypertension, and serum cholesterol). Age, education, smoking, diabetes, and hypertension were the risk factors among white and black women. Physical inactivity, nonuse of replacement hormones, serum cholesterol, and overweight were the additional risk factors among white women. Adjusted for demographic risk factors, overall PARs for study risk factors were 41.2% for white men, 60.5% for white women (with five risk factors only), 49.2% for black men, and 71.2% for black women. Much IHD mortality attributable to individual risk factors is caused by those factors in combination with other risk factors; relatively little mortality is attributable to each risk factor in isolation. Analysis that does not examine risk factor combinations may greatly overestimate PARs associated with individual risk factors.

Genotypic, clinical, and demographic characteristics of children infected with Helicobacter pylori.

Helicobacter pylori isolates vary between geographic regions. Certain H. pylori genotypes may be associated with disease outcome. Thirty-eight children underwent diagnostic upper endoscopy at four medical centers and were retrospectively analyzed to determine if H. pylori virulence genes were associated with endoscopic disease severity, histologic parameters, and host demographics. The H. pylori virulence genotype was analyzed by a reverse hybridization line probe assay and type-specific PCR. Endoscopic ulcers or erosions were found in 17 (45%) patients, with 13 (34%) of these patients having antral nodularity. Histological gastritis, of varying severity, was present in all children. Four patients harbored more than one H. pylori strain: one subject had both cagA(+) and cagA-negative strains, while three patients harbored either two different cagA-negative strains (two children) or two cagA(+) strains (one child). There were 28 (74%) cagA(+) isolates; 19 were associated with the vacA s1b genotype, 7 were associated with the vacA s1a genotype, 1 was associated with the vacA s1c genotype, and 1 was associated with the s2 genotype. Of 14 cagA-negative isolates, 6 were vacA s2 genotype, 4 were vacA s1b, 3 were vacA s1a, and 1 was vacA s1c. Nine of ten (90%) Hispanics had similar H. pylori strains (vacA s1b,m1), and all Asian-Canadian children were infected by strains with vacA s1c genotype. No correlation between H. pylori strain and endoscopic or histopathologic abnormalities was found. This study provides a baseline framework of North American children and their H. pylori strains, serving as a powerful epidemiological tool for prospective investigations to better understand the transmission and evolution of diverse disease outcomes.

Impact of changes in transportation and commuting behaviors during the 1996 Summer Olympic Games in Atlanta on air quality and childhood asthma.

CONTEXT: Vehicle exhaust is a major source of ozone and other air pollutants. Although high ground-level ozone pollution is associated with transient increases in asthma morbidity, the impact of citywide transportation changes on air quality and childhood asthma has not been studied. The alternative transportation strategy implemented during the 1996 Summer Olympic Games in Atlanta, Ga, provided such an opportunity. OBJECTIVE: To describe traffic changes in Atlanta, Ga, during the 1996 Summer Olympic Games and concomitant changes in air quality and childhood asthma events. DESIGN: Ecological study comparing the 17 days of the Olympic Games (July 19-August 4, 1996) to a baseline period consisting of the 4 weeks before and 4 weeks after the Olympic Games. SETTING AND SUBJECTS: Children aged 1 to 16 years who resided in the 5 central counties of metropolitan Atlanta and whose data were captured in 1 of 4 databases. MAIN OUTCOME MEASURES: Citywide acute care visits and hospitalizations for asthma (asthma events) and nonasthma events, concentrations of major air pollutants, meteorological variables, and traffic counts. RESULTS: During the Olympic Games, the number of asthma acute care events decreased 41.6% (4.23 vs 2.47 daily events) in the Georgia Medicaid claims file, 44.1% (1.36 vs 0.76 daily events) in a health maintenance organization database, 11.1% (4.77 vs 4.24 daily events) in 2 pediatric emergency departments, and 19.1% (2.04 vs 1.65 daily hospitalizations) in the Georgia Hospital Discharge Database. The number of nonasthma acute care events in the 4 databases changed -3.1%, +1.3%, -2.1%, and +1.0%, respectively. In multivariate regression analysis, only the reduction in asthma events recorded in the Medicaid database was significant (relative risk, 0.48; 95% confidence interval, 0.44-0.86). Peak daily ozone concentrations decreased 27.9%, from 81.3 ppb during the baseline period to 58.6 ppb during the Olympic Games (P<.001). Peak weekday morning traffic counts dropped 22.5% (P<.001). Traffic counts were significantly correlated with that day's peak ozone concentration (average r = 0.36 for all 4 roads examined). Meteorological conditions during the Olympic Games did not differ substantially from the baseline period. CONCLUSIONS: Efforts to reduce downtown traffic congestion in Atlanta during the Olympic Games resulted in decreased traffic density, especially during the critical morning period. This was associated with a prolonged reduction in ozone pollution and significantly lower rates of childhood asthma events. These data provide support for efforts to reduce air pollution and improve health via reductions in motor vehicle traffic.

Factors influencing a communitywide campaign to administer hepatitis A vaccine to men who have sex with men.

OBJECTIVES: A hepatitis A outbreak among men who have sex with men (MSM) led to a publicly funded vaccination campaign. We evaluated the MSM community's response. METHODS: A cohort of MSM from 5 community sites was surveyed. RESULTS: Thirty-four (19%) of 178 potential vaccine candidates received the vaccine during the campaign. We found a linear relation between the number of exposures to campaign information and the likelihood of vaccination (P < .001). Vaccination was independently associated with awareness of the outbreak and the vaccine, having had sexual relations with men for 12 years or longer, having recently consulted a physician, and routinely reading a local gay newspaper. CONCLUSIONS: The difficult task of vaccinating MSM can be aided by repetitive promotional messages, especially via the gay media.

Helicobacter pylori gastritis in children and adults: comparative histopathologic study.

The inflammatory response to Helicobacter pylori in adults has been well characterized. In children, studies of H. pylori gastritis have been based on small numbers of patients and have used loose definitions of the inflammatory components. Comparative study of the inflammatory response to H. pylori in children and adults can help our understanding of the natural history of this infection. Using the Updated Sydney Classification, we performed a retrospective, blinded pathology review of gastric biopsy specimens from 42 children and 40 adults with H. pylori infection, and we quantified each inflammatory cell separately (neutrophils, lymphocytes, plasma cells, and eosinophils). Differences in inflammatory cell components of children and adults were assessed by logistic regression analysis. More children had marked amounts of H. pylori (P = .05) and mild degree of neutrophils (P = .02), plasma cells (P = .005), and eosinophils (P = .0001) compared with adults. No differences existed when quantifying mononuclear cells or atrophy. Ulcers and intestinal metaplasia were present only in adults. We found that the numbers of inflammatory cells present in H. pylori-infected biopsy specimens is different in children and adults. We hypothesize that these differences demonstrate how H. pylori infection evolves from an acute childhood infection to an adult chronic disease.

Effective vaccine for lassa fever.

Lassa fever has been estimated to cause 5,000 deaths annually in West Africa. Recently, war in the zone where Lassa fever is hyperendemic has severely impeded control and treatment. Vaccination is the most viable control measure. There is no correlation between antibody levels and outcome in human patients, and inactivated vaccines produce high titers of antibodies to all viral proteins but do not prevent virus replication and death in nonhuman primates. Accordingly, we vaccinated 44 macaques with vaccinia virus-expressed Lassa virus structural proteins separately and in combination, with the object of inducing a predominantly TH1-type immune response. Following Lassa virus challenge, all unvaccinated animals died (0% survival). Nine of 10 animals vaccinated with all proteins survived (90% survival). Although no animals that received full-length glycoprotein alone had a high titer of antibody, 17 of 19 survived challenge (88%). In contrast, all animals vaccinated with nucleoprotein developed high titers of antibody but 12 of 15 died (20% survival). All animals vaccinated with single glycoproteins, G1 or G2, died, but all those that received both single glycoproteins (G1 plus G2) at separate sites survived, showing that both glycoproteins are independently important in protection. Neither group had demonstrable antibody levels prior to challenge. We demonstrate that in primates, immune responses to epitopes on both glycoproteins are required to protect against lethal challenge with Lassa virus without having untoward side effects and that this protection is likely to be primarily cell mediated. We show that an effective, safe vaccine against Lassa virus can and should be made and that its evaluation for human populations is a matter of humanitarian priority.

Multiple modes of hepatitis A virus transmission among methamphetamine users.

Methamphetamine users are at increased risk of hepatitis A, but modes of transmission are unclear. The authors conducted a case-control study among methamphetamine users during an outbreak in Iowa in 1997. Twenty-eight reported, laboratory-confirmed, hepatitis A cases did not differ from 18 susceptible controls with respect to age, sex, or number of doses used. When compared with controls in multivariate analysis, case-patients were more likely to have injected methamphetamine (odds ratio (OR) = 5.5, 95% confidence interval (CI): 1.1, 27), to have used methamphetamine with another case-patient (OR = 6.2, 95% CI: 0.95, 41), and to have used brown methamphetamine (OR = 5.5, 95% CI: 0.51, 59). Receptive needle sharing was reported by 10 of the 20 case-patients who injected. Methamphetamine use with another case-patient was also associated with hepatitis A in an analysis restricted to noninjectors (OR = 17, 95% CI: 1.0, 630). During this outbreak, hepatitis A may have been transmitted from person to person among methamphetamine users through the fecal-oral and the percutaneous routes. Methamphetamine users should be vaccinated against hepatitis A and should be given immune globulin if they used methamphetamine with a case-patient in the last 2 weeks. Persons who intend to continue using methamphetamine should be advised about safer practices.

A prolonged outbreak of Pseudomonas aeruginosa in a neonatal intensive care unit: did staff fingernails play a role in disease transmission?

OBJECTIVES: To describe an outbreak of Pseudomonas aeruginosa bloodstream infection (BSI) and endotracheal tube (ETT) colonization in a neonatal intensive care unit (NICU), determine risk factors for infection, and make preventive recommendations. DESIGN: A 15-month cohort study followed by a case-control study with an environmental survey and molecular typing of available isolates using pulsed-field gel electrophoresis. SETTING AND PATIENTS: Neonates in the NICU of a university-affiliated children's hospital. INTERVENTIONS: Improved hand washing and restriction of use of long or artificial fingernails. RESULTS: Of 439 neonates admitted during the study period, 46 (10.5%) acquired P aeruginosa; 16 (35%) of those died. Fifteen (75%) of 20 patients for whom isolates were genotyped had genotype A, and 3 (15%) had genotype B. Of 104 healthcare workers (HCWs) from whom hand cultures were obtained, P aeruginosa was isolated from three nurses. Cultures from nurses A-1 and A-2 grew genotype A, and cultures from nurse B grew genotype B. Nurse A-1 had long natural fingernails, nurse B had long artificial fingernails, and nurse A-2 had short natural fingernails. On multivariate logistic regression analysis, exposure to nurse A-1 and exposure to nurse B were each independently associated with acquiring a BSI or ETT colonization with P aeruginosa, but other variables, including exposure to nurse A-2, were not. CONCLUSION: Epidemiological evidence demonstrated an association between acquiring P aeruginosa and exposure to two nurses. Genetic and environmental evidence supported that association and suggested, but did not prove, a possible role for long or artificial fingernails in the colonization of HCWs' hands with P aeruginosa. Requiring short natural fingernails in NICUs is a reasonable policy that might reduce the incidence of hospital-acquired infections.

Outbreak of histoplasmosis among cavers attending the National Speleological Society Annual Convention, Texas, 1994.

In June 1994, 18 people developed serologically confirmed histoplasmosis following cave exploration associated with the annual National Speleological Society Convention in Bracketville, Texas. Six others had an undiagnosed illness suspected to be histoplasmosis. Two persons were hospitalized. We conducted a survey of convention attendees and a nested case-control study of those entering caves. We also conducted a histoplasmin skin test survey of a subgroup of the society, the Texas Cavers Association, who were attending a reunion in October 1994. Among the national convention attendees, exposure to two caves was identified as responsible for 22 (92%) of the 24 cases; 12 (75%) of 16 people exploring one cave (Cave A) and 10 (77%) of 13 exploring a separate cave (Cave B) developed acute histoplasmosis. Additional risk-factors included fewer years of caving experience, longer time spent in the caves, and entering a confined crawl space in Cave A. Of 113 participants in the separate skin test survey, 68 (60%) were found to be skin test positive, indicating previous exposure to Histoplasma capsulatum. A positive skin test was significantly associated with male sex and more years of caving experience. Those less experienced in caving associations should be taught about histoplasmosis, and health care providers should pursue histories of cave exposure for patients with bronchitis or pneumonia that does not respond to initial antibiotic therapy.

First do no harm: making oral rehydration solution safer in a cholera epidemic.

Oral rehydration solution (ORS) is lifesaving therapy for cholera and pediatric diarrhea. During a cholera epidemic in Guinea-Bissau, we evaluated the microbiologic quality of ORS prepared at a hospital and tested a simple intervention using special vessels for disinfecting tap water with bleach and for preparing, storing, and dispensing ORS. Few coliform bacteria and Escherichia coli were recovered from tap water; however, pre-intervention ORS contained numerous bacteria including E. coli and toxigenic Vibrio cholerae O1. In contrast, ORS samples from intervention vessels had few or no coliform bacteria, no E. coli, and no V. cholerae. Mean pre-intervention counts of coliform bacteria (3.4 x 10(7) colony-forming units [cfu]/100 ml) and E. coli (6.2 x 10(3) cfu) decreased significantly during the intervention period to 3.6 x 10(2) cfu and 0 cfu, respectively (P < 0.001). This simple system using bleach disinfectant and special storage vessels prevents bacterial contamination of ORS and reduces the risk of nosocomial transmission of cholera and other enteric pathogens.

PIP: This paper evaluates the microbiologic quality of oral rehydration solution (ORS) prepared at a hospital during a cholera epidemic in Guinea-Bissau. The study tested a simple intervention using special vessels for disinfecting tap water with bleach and for preparing, storing, and dispensing ORS. Subjects included approximately 80% of the cholera patients seeking treatment, who were referred to the cholera ward of Simao-Mendes National Hospital. Results suggest that only few coliform bacteria and Escherichia coli were recovered from tap water; however, pre-intervention ORS contained numerous bacteria including E. coli and toxigenic Vibrio cholerae O1. In contrast, ORS samples from intervention vessels had few or no coliform bacteria, no E. coli, and no V. cholerae. This simple system using bleach disinfectant and special storage vessels prevents bacterial contamination of ORS and reduces the risk of nosocomial transmission of cholera and other enteric pathogens.

A massive epidemic of multidrug-resistant typhoid fever in Tajikistan associated with consumption of municipal water.

From 1 January through 30 June 1997, 8901 cases of typhoid fever and 95 associated deaths were reported in Dushanbe, Tajikistan. Of 29 Salmonella serotype Typhi isolates tested, 27 (93%) were resistant to ampicillin, chloramphenicol, nalidixic acid, streptomycin, sulfisoxazole, tetracycline, and trimethoprim-sulfamethoxazole. In a case-control study of 45 patients and 123 controls, Salmonella Typhi infection was associated with drinking unboiled water (matched odds ratio, 7; 95% confidence interval, 3-24; P<.001). Of tap water samples, 97% showed fecal coliform contamination (mean level, 175 cfu/100 mL). Samples taken from water treatment plants revealed that fecal coliform contamination occurred both before and after treatment. Lack of chlorination, equipment failure, and back-siphonage in the water distribution system led to contamination of drinking water. After chlorination and coagulation were begun at the treatment plants and a water conservation campaign was initiated to improve water pressure, the incidence of typhoid fever declined dramatically.

Diarrhoea prevention in Bolivia through point-of-use water treatment and safe storage: a promising new strategy.

A novel water quality intervention that consists of point-of-use water disinfection, safe storage and community education was field tested in Bolivia. A total of 127 households in two periurban communities were randomized into intervention and control groups, surveyed and the intervention was distributed. Monthly water quality testing and weekly diarrhoea surveillance were conducted. Over a 5-month period, intervention households had 44% fewer diarrhoea episodes than control households (P = 0.002). Infants < 1 year old (P = 0.05) and children 5-14 years old (P = 0.01) in intervention households had significantly less diarrhoea than control children. Campylobacter was less commonly isolated from intervention than control patients (P = 0.02). Stored water in intervention households was less contaminated with Escherichia coli than stored water in control households (P < 0.0001). Intervention households exhibited less E. coli contamination of stored water and less diarrhoea than control households. This promising new strategy may have broad applicability for waterborne disease prevention.

Consequences in Georgia of a nationwide outbreak of Salmonella infections: what you don't know might hurt you.

OBJECTIVES: This study assessed the impact in Georgia of a nationwide salmonellosis outbreak caused by ice cream products and the effectiveness of the subsequent warning against eating the implicated products. METHODS: A telephone survey of 250 randomly selected Georgia customers of the ice cream producer was conducted 13 to 17 days after the warning. RESULTS: Respondents from 179 households representing 628 persons were interviewed. The median date of first hearing the warning was 5 days after it was issued, and 16 respondents (9%) had not heard it. Among those who had heard the warning, 42 (26%) did not initially believe the products were unsafe. In 22 (31%) of the 72 households that had the implicated ice cream when the respondent heard the warning, someone subsequently ate the ice cream. Diarrhea was reported in 26% (121/463) of persons who had eaten the products but in only 5% (8/152) who had not (odds ratio [controlling for household clustering] = 3.8; 95% confidence interval = 2.0, 7.5). We estimate this outbreak caused 11,000 cases of diarrhea in Georgia, 1760 (16%) with exposure after the warning. CONCLUSIONS: A large outbreak occurred in Georgia, much of which might have been prevented by a more timely and convincing warning.

Cryptococcosis: population-based multistate active surveillance and risk factors in human immunodeficiency virus-infected persons. Cryptococcal Active Surveillance Group.

To determine the incidence of cryptococcosis and its risk factors among human immunodeficiency virus (HIV)-infected persons, population-based active surveillance was conducted in four US areas (population, 12.5 million) during 1992-1994, and a case-control study was done. Of 1083 cases, 931 (86%) occurred in HIV-infected persons. The annual incidence of cryptococcosis per 1000 among persons living with AIDS ranged from 17 (San Francisco, 1994) to 66 (Atlanta, 1992) and decreased significantly in these cities during 1992-1994. Among non-HIV-infected persons, the annual incidence of cryptococcosis ranged from 0.2 to 0.9/100,000. Multivariate analysis of the case-control study (158 cases and 423 controls) revealed smoking and outdoor occupations to be significantly associated with an increased risk of cryptococcosis; receiving fluconazole within 3 months before enrollment was associated with a decreased risk for cryptococcosis. Further studies are needed to better describe persons with AIDS currently developing cryptococcosis in the era of highly active antiretroviral therapy.

The role of Gulf Coast oysters harvested in warmer months in Vibrio vulnificus infections in the United States, 1988-1996. Vibrio Working Group.

Vibrio vulnificus infections are highly lethal and associated with consumption of raw shellfish and exposure of wounds to seawater. V. vulnificus infections were reported to the Centers for Disease Control and Prevention from 23 states. For primary septicemia infections, oyster trace-backs were performed and water temperature data obtained at harvesting sites. Between 1988 and 1996, 422 infections were reported; 45% were wound infections, 43% primary septicemia, 5% gastroenteritis, and 7% from undetermined exposure. Eighty-six percent of patients were male, and 96% with primary septicemia consumed raw oysters. Sixty-one percent with primary septicemia died; underlying liver disease was associated with fatal outcome. All trace-backs with complete information implicated oysters harvested in the Gulf of Mexico; 89% were harvested in water >22 degrees C, the mean annual temperature at the harvesting sites (P < .0001). Control measures should focus on the increased risk from oysters harvested from the Gulf of Mexico during warm months as well as education about host susceptibility factors.

Reduction of fecal contamination of street-vended beverages in Guatemala by a simple system for water purification and storage, handwashing, and beverage storage.

Street-vended foods and beverages, an integral part of urban economies in the developing world, have been implicated in cholera transmission in Latin America. To improve the microbiologic quality of market-vended beverages in Guatemala, we tested a simple system consisting of dilute bleach (4.95% free available chlorine) for water purification, narrow-mouth plastic vessels with spigots for disinfecting and storing water and for preparing and storing beverages, handwashing soap, and education in using the system. We conducted a randomized controlled intervention trial among 41 vendors who received the intervention and 42 control vendors, comparing total and fecal coliform bacteria and Escherichia coli contamination of market-vended beverages, stored water, and vendors' hands. Samples were obtained at baseline and at each of six weekly follow-up visits. At baseline, fecal coliform bacteria were found in 40 (48%) market-vended beverages and E. coli in 14 (17%). When compared with samples from control vendors, a significant decrease in total coliform (P < 0.001) and fecal coliform (P < 0.001) bacteria in samples of stored water and beverages sold by intervention vendors was observed over the course of the study. The vessel system was well accepted by vendors. This simple inexpensive system consisting of hypochlorite disinfectant, plastic vessels, soap, and education can significantly reduce fecal contamination of market-vended beverages.

An outbreak of Escherichia coli O157:H7 infections associated with leaf lettuce consumption.

In July 1995, 40 Montana residents were identified with laboratory-confirmed Escherichia coli O157:H7 infection; 52 residents had bloody diarrhea without laboratory confirmation. The median age of those with laboratory-confirmed cases was 42 years (range, 4- 86); 58% were female. Thirteen patients were hospitalized, and 1 developed hemolytic-uremic syndrome. A case-control study showed that 19 (70%) of 27 patients but only 8 (17%) of 46 controls reported eating purchased (not home-grown) leaf lettuce before illness (matched odds ratio, 25.3; 95% confidence interval, 3.9-1065.6). Pulsed-field gel electrophoresis identified a common strain among 22 of 23 isolates tested. Implicated lettuce was traced to two sources: a local Montana farm and six farms in Washington State that shipped under the same label. This outbreak highlights the increasing importance of fresh produce as a vehicle in foodborne illness. Sanitary growing and handling procedures are necessary to prevent these infections.

An outbreak of salmonellosis among children attending a reptile exhibit at a zoo.

OBJECTIVE: In January 1996, an outbreak of diarrhea caused by Salmonella Enteritidis occurred in children attending a Komodo dragon exhibit at a metropolitan zoo. We sought to determine the extent of the outbreak and mode of transmission. STUDY DESIGN: A case-control study was conducted. Controls were randomly selected from zoo membership lists and matched to patients by age group and date of exhibit visit. RESULTS: Of 65 patients identified, 39 had confirmed and 26 had suspected cases. The median age was 7 years (range, 3 months to 48 years); 55% were enrolled in the case-control study. No patients and two (4%) controls reported touching a dragon; however, 83% of patients but only 52% of controls touched the wooden barrier that surrounded the dragon pen (odds ratio = 4.0, 95% CI 1.2 to 13.9). Washing hands at the zoo after visiting the dragons was highly protective (OR = 0.14, 95% CI 0.03 to 0.7). Cultures from the patients, one dragon, and the exhibit barriers yielded Salmonella Enteritidis, phage type 8. On the basis of an attack rate of 4.3% among exhibit attendees under 13 years old on whom data were collected, we estimate that 315 additional cases of salmonellosis occurred among visitors in this age group. CONCLUSION: This large outbreak demonstrates the importance of environmental contamination in the transmission of Salmonella from reptiles, and the protective value of hand washing. Recommendations regarding reptile exhibits and reptilian pets should emphasize this indirect route.