Robert M. Hoekstra

FOODBORNE ILLNESS ACQUIRED IN THE UNITED STATES-MAJOR PATHOGENS

Each year, 31 pathogens caused 9.4 million episodes of foodborne illness, resulting in 55,961 hospitalizations and 1,351 deaths.

Non-O157 Shiga Toxin–Producing Escherichia coli Infections in the United States, 1983–2002

BACKGROUND Shiga toxin-producing Escherichia coli (STEC) O157:H7 is a well-recognized cause of bloody diarrhea and hemolytic-uremic syndrome (HUS). Non-O157 STEC contribute to this burden of illness but have been underrecognized as a result of diagnostic limitations and inadequate surveillance. METHODS Between 1983 and 2002, 43 state public health laboratories submitted 940 human non-O157 STEC isolates from persons with sporadic illnesses to the Centers for Diseases Control and Prevention reference laboratory for confirmation and serotyping. RESULTS The most common serogroups were O26 (22%), O111 (16%), O103 (12%), O121 (8%), O45 (7%), and O145 (5%). Non-O157 STEC infections were most frequent during the summer and among young persons (median age, 12 years; interquartile range, 3-37 years). Virulence gene profiles were as follows: 61% stx(1) but not stx(2); 22% stx(2) but not stx(1); 17% both stx(1) and stx(2); 84% intimin (eae); and 86% enterohemolysin (E-hly). stx(2) was strongly associated with an increased risk of HUS, and eae was strongly associated with an increased risk of bloody diarrhea. STEC O111 accounted for most cases of HUS and was also the cause of 3 of 7 non-O157 STEC outbreaks reported in the United States. CONCLUSIONS Non-O157 STEC can cause severe illness that is comparable to the illness caused by STEC O157. Strains that produce Shiga toxin 2 are much more likely to cause HUS than are those that produce Shiga toxin 1 alone. Improving surveillance will more fully elucidate the incidence and pathological spectrum of these emerging agents. These efforts require increased clinical suspicion, improved clinical laboratory isolation, and continued serotyping of isolates in public health laboratories.

Foodborne Illness Acquired in the United States—Unspecified Agents

Each year, unspecified agents caused an estimated 38.4 million episodes of illness, resulting in 71,878 hospitalizations and 1,686 deaths.

Attribution of foodborne illnesses, hospitalizations, and deaths to food commodities by using outbreak data, United States, 1998-2008.

Each year, >9 million foodborne illnesses are estimated to be caused by major pathogens acquired in the United States. Preventing these illnesses is challenging because resources are limited and linking individual illnesses to a particular food is rarely possible except during an outbreak. We developed a method of attributing illnesses to food commodities that uses data from outbreaks associated with both simple and complex foods. Using data from outbreak-associated illnesses for 1998–2008, we estimated annual US foodborne illnesses, hospitalizations, and deaths attributable to each of 17 food commodities. We attributed 46% of illnesses to produce and found that more deaths were attributed to poultry than to any other commodity. To the extent that these estimates reflect the commodities causing all foodborne illness, they indicate that efforts are particularly needed to prevent contamination of produce and poultry. Methods to incorporate data from other sources are needed to improve attribution estimates for some commodities and agents.

Effect of handwashing on child health: a randomised controlled trial.

BACKGROUND More than 3.5 million children aged less than 5 years die from diarrhoea and acute lower respiratory-tract infection every year. We undertook a randomised controlled trial to assess the effect of handwashing promotion with soap on the incidence of acute respiratory infection, impetigo, and diarrhoea. METHODS In adjoining squatter settlements in Karachi, Pakistan, we randomly assigned 25 neighbourhoods to handwashing promotion; 11 neighbourhoods (306 households) were randomised as controls. In neighbourhoods with handwashing promotion, 300 households each were assigned to antibacterial soap containing 1.2% triclocarban and to plain soap. Fieldworkers visited households weekly for 1 year to encourage handwashing by residents in soap households and to record symptoms in all households. Primary study outcomes were diarrhoea, impetigo, and acute respiratory-tract infections (ie, the number of new episodes of illness per person-weeks at risk). Pneumonia was defined according to the WHO clinical case definition. Analysis was by intention to treat. FINDINGS Children younger than 5 years in households that received plain soap and handwashing promotion had a 50% lower incidence of pneumonia than controls (95% CI (-65% to -34%). Also compared with controls, children younger than 15 years in households with plain soap had a 53% lower incidence of diarrhoea (-65% to -41%) and a 34% lower incidence of impetigo (-52% to -16%). Incidence of disease did not differ significantly between households given plain soap compared with those given antibacterial soap. INTERPRETATION Handwashing with soap prevents the two clinical syndromes that cause the largest number of childhood deaths globally-namely, diarrhoea and acute lower respiratory infections. Handwashing with daily bathing also prevents impetigo.

Risk Factors for Sporadic Campylobacter Infection in the United States: A Case-Control Study in FoodNet Sites

Campylobacter is a common cause of gastroenteritis in the United States. We conducted a population-based case-control study to determine risk factors for sporadic Campylobacter infection. During a 12-month study, we enrolled 1316 patients with culture-confirmed Campylobacter infections from 7 states, collecting demographic, clinical, and exposure data using a standardized questionnaire. We interviewed 1 matched control subject for each case patient. Thirteen percent of patients had traveled abroad. In multivariate analysis of persons who had not traveled, the largest population attributable fraction (PAF) of 24% was related to consumption of chicken prepared at a restaurant. The PAF for consumption of nonpoultry meat that was prepared at a restaurant was also large (21%); smaller proportions of illness were associated with other food and nonfood exposures. Efforts to reduce contamination of poultry with Campylobacter should benefit public health. Restaurants should improve food-handling practices, ensure adequate cooking of meat and poultry, and consider purchasing poultry that has been treated to reduce Campylobacter contamination.

Recurrent multistate outbreak of Salmonella Newport associated with tomatoes from contaminated fields, 2005

Salmonella Newport causes more than an estimated 100,000 infections annually in the United States. In 2002, tomatoes grown and packed on the eastern shore of Virginia contaminated with a pan-susceptible S. Newport strain caused illness in 510 patients in 26 states. In July-November 2005, the same strain caused illness in at least 72 patients in 16 states. We conducted a case-control study during the 2005 outbreak, enrolling 29 cases and 140 matched neighbourhood controls. Infection was associated with eating tomatoes (matched odds ratio 9.7, 95% confidence interval 3.3-34.9). Tomatoes were traced back to the eastern shore of Virginia, where the outbreak strain was isolated from pond water used to irrigate tomato fields. Two multistate outbreaks caused by one rare strain, and identification of that strain in irrigation ponds 2 years apart, suggest persistent contamination of tomato fields. Further efforts are needed to prevent produce contamination on farms and throughout the food supply chain.

Prolonged Diarrhea Due to Ciprofloxacin-Resistant Campylobacter Infection

BACKGROUND Campylobacter causes >1 million infections annually in the United States. Fluoroquinolones (e.g., ciprofloxacin) are used to treat Campylobacter infections in adults. Although human infections with ciprofloxacin-resistant Campylobacter have become increasingly common, the human health consequences of such infections are not well described. METHODS A case-control study of persons with sporadic Campylobacter infection was conducted within 7 FoodNet sites during 1998-1999. The E-test system (AB Biodisk) was used to test for antimicrobial susceptibility to ciprofloxacin; ciprofloxacin resistance was defined as a ciprofloxacin minimum inhibitory concentration of > or =4 microg/mL. We conducted a case-comparison study of interviewed persons who had an isolate tested. RESULTS Of 858 isolates tested, 94 (11%) were ciprofloxacin resistant. Among 290 persons with Campylobacter infection who did not take antidiarrheal medications, persons with ciprofloxacin-resistant infection had a longer mean duration of diarrhea than did persons with ciprofloxacin-susceptible infection (9 vs. 7 days [P=.04]). This difference was even more pronounced among the 63 persons who did not take antidiarrheal medications or antimicrobial agents (12 vs. 6 days [P=.04]). In a multivariable analysis-of-variance model, the persons with ciprofloxacin-resistant infection had a longer mean duration of diarrhea than did the persons with ciprofloxacin-susceptible infection (P=.01); this effect was independent of foreign travel. The association between ciprofloxacin resistance and prolonged diarrhea is consistent across a variety of analytical approaches. CONCLUSIONS Persons with ciprofloxacin-resistant Campylobacter infection have a longer duration of diarrhea than do persons with ciprofloxacin-susceptible Campylobacter infection. Additional efforts are needed to preserve the efficacy of fluoroquinolones.

Listeria monocytogenes Infection from Foods Prepared in a Commercial Establishment: A Case-Control Study of Potential Sources of Sporadic Illness in the United States

BACKGROUND Listeria monocytogenes has been estimated to cause >2500 illnesses and 500 deaths annually in the United States. Efforts to reduce foodborne listeriosis have focused on foods frequently implicated in outbreaks. Potential sources for L. monocytogenes infection not associated with outbreaks remain poorly understood. METHODS The Foodborne Diseases Active Surveillance Network conducts surveillance for culture-confirmed listeriosis at clinical laboratories in 9 states. After excluding outbreak-associated cases, we attempted to enroll eligible case patients with L. monocytogenes infection in a case-control study from 2000 through 2003. Control subjects were recruited through health care providers and were matched to case patients by state, age, and immunosuppression status. Data were collected about exposures occurring in the 4 weeks before specimen collection from the case patients. RESULTS Of the 249 case patients with L. monocytogenes infection, only 12 (5%) had cases that were associated with outbreaks; 6 other patients were ineligible for other reasons. Of 231 eligible case patients, 169 (73%) were enrolled in the study. We classified 28 case patients as having pregnancy-associated cases. We enrolled 376 control subjects. In multivariable analysis, L. monocytogenes infection was associated with eating melons at a commercial establishment (odds ratio, 2.6; 95% confidence interval, 1.4-5.0) and eating hummus prepared in a commercial establishment (odds ratio, 5.7; 95% confidence interval, 1.7-19.1). CONCLUSIONS Most cases of L. monocytogenes infection were not associated with outbreaks. Reducing the burden of foodborne listeriosis may require interventions directed at retail environments and at foods, such as melons and hummus, that are not commonly recognized as high risk. Because of the severity of listeriosis, pregnant women and other persons at risk may wish to avoid eating these newly implicated foods.

Combining drinking water treatment and hand washing for diarrhoea prevention, a cluster randomised controlled trial

Objectives  To evaluate the effectiveness of point of use water treatment with flocculent‐disinfectant on reducing diarrhoea and the additional benefit of promoting hand washing with soap.