L. Hannah Gould

Epidemiology of Community-Associated Clostridium difficile Infection, 2009 Through 2011

IMPORTANCE Clostridium difficile infection (CDI) has been increasingly reported among healthy individuals in the community. Recent data suggest that community-associated CDI represents one-third of all C difficile cases. The epidemiology and potential sources of C difficile in the community are not fully understood. OBJECTIVES To determine epidemiological and clinical characteristics of community-associated CDI and to explore potential sources of C difficile acquisition in the community. DESIGN AND SETTING Active population-based and laboratory-based CDI surveillance in 8 US states. PARTICIPANTS Medical records were reviewed and interviews performed to assess outpatient, household, and food exposures among patients with community-associated CDI (ie, toxin or molecular assay positive for C difficile and no overnight stay in a health care facility within 12 weeks). Molecular characterization of C difficile isolates was performed. Outpatient health care exposure in the prior 12 weeks among patients with community-associated CDI was a priori categorized into the following 3 levels: no exposure, low-level exposure (ie, outpatient visit with physician or dentist), or high-level exposure (ie, surgery, dialysis, emergency or urgent care visit, inpatient care with no overnight stay, or health care personnel with direct patient care). MAIN OUTCOMES AND MEASURES Prevalence of outpatient health care exposure among patients with community-associated CDI and identification of potential sources of C difficile by level of outpatient health care exposure. RESULTS Of 984 patients with community-associated CDI, 353 (35.9%) did not receive antibiotics, 177 (18.0%) had no outpatient health care exposure, and 400 (40.7%) had low-level outpatient health care exposure. Thirty-one percent of patients without antibiotic exposure received proton pump inhibitors. Patients having CDI with no or low-level outpatient health care exposure were more likely to be exposed to infants younger than 1 year (P = .04) and to household members with active CDI (P = .05) compared with those having high-level outpatient health care exposure. No association between food exposure or animal exposure and level of outpatient health care exposure was observed. North American pulsed-field gel electrophoresis (NAP) 1 was the most common (21.7%) strain isolated; NAP7 and NAP8 were uncommon (6.7%). CONCLUSIONS AND RELEVANCE Most patients with community-associated CDI had recent outpatient health care exposure, and up to 36% would not be prevented by reduction of antibiotic use only. Our data support evaluation of additional strategies, including further examination of C difficile transmission in outpatient and household settings and reduction of proton pump inhibitor use.

Increased Recognition of Non-O157 Shiga Toxin–Producing Escherichia coli Infections in the United States During 2000–2010: Epidemiologic Features and Comparison with E. coli O157 Infections

BACKGROUND Shiga toxin-producing Escherichia coli (STEC) are an important cause of diarrhea and the major cause of postdiarrheal hemolytic uremic syndrome. Non-O157 STEC infections are being recognized with greater frequency because of changing laboratory practices. METHODS Foodborne Diseases Active Surveillance Network (FoodNet) site staff conducted active, population-based surveillance for laboratory-confirmed STEC infections. We assessed frequency and incidence of STEC infections by serogroup and examined and compared demographic factors, clinical characteristics, and frequency of international travel among patients. RESULTS During 2000-2010, FoodNet sites reported 2006 cases of non-O157 STEC infection and 5688 cases of O157 STEC infections. The number of reported non-O157 STEC infections increased from an incidence of 0.12 per 100,000 population in 2000 to 0.95 per 100,000 in 2010; while the rate of O157 STEC infections decreased from 2.17 to 0.95 per 100,000. Among non-O157 STEC, six serogroups were most commonly reported: O26 (26%), O103 (22%), O111 (19%), O121 (6%), O45 (5%), and O145 (4%). Non-O157 STEC infections were more common among Hispanics, and infections were less severe than those caused by O157 STEC, but this varied by serogroup. Fewer non-O157 STEC infections were associated with outbreaks (7% versus 20% for O157), while more were associated with international travel (14% versus 3% for O157). CONCLUSIONS Improved understanding of the epidemiologic features of non-O157 STEC infections can inform food safety and other prevention efforts. To detect both O157 and non-O157 STEC infections, clinical laboratories should routinely and simultaneously test all stool specimens submitted for diagnosis of acute community-acquired diarrhea for O157 STEC and for Shiga toxin and ensure that isolates are sent to a public health laboratory for serotyping and subtyping.

Hemolytic Uremic Syndrome and Death in Persons with Escherichia coli O157:H7 Infection, Foodborne Diseases Active Surveillance Network Sites, 2000-2006

BACKGROUND Hemolytic uremic syndrome (HUS) is a life-threatening illness usually caused by infection with Shiga toxin-producing Escherichia coli O157 (STEC O157). We evaluated the age-specific rate of HUS and death among persons with STEC O157 infection and the risk factors associated with developing HUS. METHODS STEC O157 infections and HUS cases were reported from 8 sites participating in the Foodborne Diseases Active Surveillance Network during 2000-2006. For each case of STEC O157 infection and HUS, demographic and clinical outcomes were reported. The proportion of STEC O157 infections resulting in HUS was determined. RESULTS A total of 3464 STEC O157 infections were ascertained; 218 persons (6.3%) developed HUS. The highest proportion of HUS cases (15.3%) occurred among children aged <5 years. Death occurred in 0.6% of all patients with STEC O157 infection and in 4.6% of those with HUS. With or without HUS, persons aged 60 years had the highest rate of death due to STEC O157 infection. Twelve (3.1%) of 390 persons aged 60 years died, including 5 (33.3%) of 15 persons with HUS and 7 (1.9%) of 375 without. Among children aged <5 years, death occurred in 4 (3.0%) of those with HUS and 2 (0.3%) of those without. CONCLUSIONS Young children and females had an increased risk of HUS after STEC O157 infection. With or without HUS, elderly persons had the highest proportion of deaths associated with STEC O157 infection. These data support recommendations for aggressive supportive care of young children and the elderly early during illness due to STEC O157.

Epidemiology of Foodborne Norovirus Outbreaks, United States, 2001–2008

In the United States, the leading cause of foodborne illness is norovirus; an average of 1 foodborne norovirus outbreak is reported every day. The more we know about how this virus is spread and in which foods, the better we can ward off future outbreaks. A recent study identified the most common sources of foodborne norovirus outbreaks as ready-to-eat foods that contain fresh produce and mollusks that are eaten raw, such as oysters. Most implicated foods had been prepared in restaurants, delicatessens, and other commercial settings and were most often contaminated by an infected food worker. Although possible contamination during production, harvesting, or processing cannot be overlooked, food safety during meal preparation should be emphasized. Food handlers should wash their hands, avoid bare-handed contact with ready-to-eat foods, and not work when they are sick.

Clostridium difficile in Food and Domestic Animals: A New Foodborne Pathogen?

Clostridium difficile infection is increasingly recognized as a cause of diarrhea in outpatients and persons with no apparent health care facility contacts. In contrast to C. difficile infection acquired in health care settings, few risk factors for development of community-associated C. difficile infection are known. Foodborne transmission of C. difficile has been hypothesized as a possible source for community-associated infections; however, the evidence to confirm or refute this hypothesis is incomplete. Recent studies have demonstrated isolation of C. difficile from foods in the United States, Canada, and Europe and from meat products intended for consumption by pets. This raises questions about foodborne transmission of this pathogen to humans through consumption of contaminated products. This review summarizes the available data on C. difficile in animals and food and discusses the potential for foodborne transmission of this pathogen.

An Investigation of a Major Outbreak of Rift Valley Fever in Kenya: 2006–2007

An outbreak of Rift Valley fever (RVF) occurred in Kenya during November 2006 through March 2007. We characterized the magnitude of the outbreak through disease surveillance and serosurveys, and investigated contributing factors to enhance strategies for forecasting to prevent or minimize the impact of future outbreaks. Of 700 suspected cases, 392 met probable or confirmed case definitions; demographic data were available for 340 (87%), including 90 (26.4%) deaths. Male cases were more likely to die than females, Case Fatality Rate Ratio 1.8 (95% Confidence Interval [CI] 1.3-3.8). Serosurveys suggested an attack rate up to 13% of residents in heavily affected areas. Genetic sequencing showed high homology among viruses from this and earlier RVF outbreaks. Case areas were more likely than non-case areas to have soil types that retain surface moisture. The outbreak had a devastatingly high case-fatality rate for hospitalized patients. However, there were up to 180,000 infected mildly ill or asymptomatic people within highly affected areas. Soil type data may add specificity to climate-based forecasting models for RVF.

Acute Gastroenteritis Surveillance through the National Outbreak Reporting System, United States

Implemented in 2009, the National Outbreak Reporting System provides surveillance for acute gastroenteritis outbreaks in the United States resulting from any transmission mode. Data from the first 2 years of surveillance highlight the predominant role of norovirus. The pathogen-specific transmission pathways and exposure settings identified can help inform prevention efforts.

Foodborne Disease Outbreaks caused by Bacillus cereus, Clostridium perfringens, and Staphylococcus aureus, United States, 1998–2008

From 1998 to 2008, 1229 foodborne outbreaks caused by Bacillus cereus, Clostridium perfringens, and Staphylococcus aureus were reported in the United States; 39% were reported with a confirmed etiology. Vomiting was commonly reported in B. cereus (median, 75% of cases) and S. aureus outbreaks (median, 87%), but rarely in C. perfringens outbreaks (median, 9%). Meat or poultry dishes were commonly implicated in C. perfringens (63%) and S. aureus (55%) outbreaks, and rice dishes were commonly implicated in B. cereus outbreaks (50%). Errors in food processing and preparation were commonly reported (93%), regardless of etiology; contamination by a food worker was only common in S. aureus outbreaks (55%). Public health interventions should focus on these commonly reported errors to reduce the occurrence of outbreaks caused by B. cereus, C. perfringens, and S. aureus in the United States.

Implementation of Nationwide Real-time Whole-genome Sequencing to Enhance Listeriosis Outbreak Detection and Investigation

Listeria monocytogenes (Lm) causes severe foodborne illness (listeriosis). Previous molecular subtyping methods, such as pulsed-field gel electrophoresis (PFGE), were critical in detecting outbreaks that led to food safety improvements and declining incidence, but PFGE provides limited genetic resolution. A multiagency collaboration began performing real-time, whole-genome sequencing (WGS) on all US Lm isolates from patients, food, and the environment in September 2013, posting sequencing data into a public repository. Compared with the year before the project began, WGS, combined with epidemiologic and product trace-back data, detected more listeriosis clusters and solved more outbreaks (2 outbreaks in pre-WGS year, 5 in WGS year 1, and 9 in year 2). Whole-genome multilocus sequence typing and single nucleotide polymorphism analyses provided equivalent phylogenetic relationships relevant to investigations; results were most useful when interpreted in context of epidemiological data. WGS has transformed listeriosis outbreak surveillance and is being implemented for other foodborne pathogens.

Risk Factors for Severe Rift Valley Fever Infection in Kenya, 2007

A large Rift Valley fever (RVF) outbreak occurred in Kenya from December 2006 to March 2007. We conducted a study to define risk factors associated with infection and severe disease. A total of 861 individuals from 424 households were enrolled. Two hundred and two participants (23%) had serologic evidence of acute RVF infection. Of these, 52 (26%) had severe RVF disease characterized by hemorrhagic manifestations or death. Independent risk factors for acute RVF infection were consuming or handling products from sick animals (odds ratio [OR] = 2.53, 95% confidence interval [CI] = 1.78-3.61, population attributable risk percentage [PAR%] = 19%) and being a herds person (OR 1.77, 95% CI = 1.20-2.63, PAR% = 11%). Touching an aborted animal fetus was associated with severe RVF disease (OR = 3.83, 95% CI = 1.68-9.07, PAR% = 14%). Consuming or handling products from sick animals was associated with death (OR = 3.67, 95% CI = 1.07-12.64, PAR% = 47%). Exposures related to animal contact were associated with acute RVF infection, whereas exposures to mosquitoes were not independent risk factors.