Syndromic Gastrointestinal Panel Diagnostic Tests Have Changed our Understanding of the Epidemiology of Yersiniosis-Foodborne Diseases Active Surveillance Network, 2010-2021.

Background: In the US, yersinosis was understood to predominantly occur in winter and among Black or African American infants and Asian children. Increased use of culture-independent diagnostic tests (CIDTs) has led to marked increases in yersinosis diagnoses. Methods: We describe differences in the epidemiology of yersiniosis diagnosed by CIDT versus culture in 10 US sites, and identify determinants of health associated with diagnostic method. Results: Annual reported incidence increased from 0.3/100 000 in 2010 to 1.3/100 000 in 2021, particularly among adults ≥18 years, regardless of race and ethnicity, and during summer months. The proportion of CIDT-diagnosed infections increased from 3% in 2012 to 89% in 2021. An ill person's demographic characteristics and location of residence had a significant impact on their odds of being diagnosed by CIDT. Conclusions: Improved detection due to increased CIDT use has altered our understanding of yersinosis epidemiology, however differential access to CIDTs may still affect our understanding of yersinosis.

Cronobacter sakazakii Infections in Two Infants Linked to Powdered Infant Formula and Breast Pump Equipment - United States, 2021 and 2022.

Cronobacter sakazakii, a species of gram-negative bacteria belonging to the Enterobacteriaceae family, is known to cause severe and often fatal meningitis and sepsis in young infants. C. sakazakii is ubiquitous in the environment, and most reported infant cases have been attributed to contaminated powdered infant formula (powdered formula) or breast milk that was expressed using contaminated breast pump equipment (1-3). Previous investigations of cases and outbreaks have identified C. sakazakii in opened powdered formula, breast pump parts, environmental surfaces in the home, and, rarely, in unopened powdered formula and formula manufacturing facilities (2,4-6). This report describes two infants with C. sakazakii meningitis reported to CDC in September 2021 and February 2022. CDC used whole genome sequencing (WGS) analysis to link one case to contaminated opened powdered formula from the patient's home and the other to contaminated breast pump equipment. These cases highlight the importance of expanding awareness about C. sakazakii infections in infants, safe preparation and storage of powdered formula, proper cleaning and sanitizing of breast pump equipment, and using WGS as a tool for C. sakazakii investigations.

Differences in risk factors for transmission among Shiga toxin-producing Escherichia coli serogroups and stx profiles.

OBJECTIVES: Trends in the incidence of O157 and non-O157 serogroups of Shiga toxin-producing Escherichia coli (STEC) infections have markedly diverged. Here, we estimate the extent to which STEC serogroups share the same transmission routes and risk factors, potentially explaining these trends. METHODS: With 3048 STEC cases reported in Minnesota from 2010 to 2019, we used lasso penalized regression to estimate pooled odds ratios (pOR) for the association between STEC risk factors and specific STEC serogroups and Shiga toxin gene profiles. We used random forests as a confirmatory analysis. RESULTS: Across an extended period of time, we found evidence for person-to-person transmission associated with the O26 serogroup, relative to other serogroups (pOR = 1.32 for contact with an individual with diarrhea). Rurality was less associated with non-O157 serogroups than O157 (pOR = 1.21 for each increasing level of rurality). We also found an association between unpasteurized juice and strains carrying only stx1 (pOR = 1.41). CONCLUSIONS: Collectively, these results show differences in risk factors across STEC types, which suggest differences in the most effective routes of transmission. Serogroup-specific disease control strategies should be explored. Specifically, preventative measures for non-O157 STEC need to extend beyond those we have employed for O157 STEC.

Outbreak of Norovirus Gastroenteritis Associated With Ice Cream Contaminated by Frozen Raspberries From China-Minnesota, United States, 2016.

BACKGROUND: Norovirus is the etiology for about 60% of foodborne outbreaks identified in Minnesota. Contamination of food during preparation by food handlers is by far the most common cause of these outbreaks. Norovirus outbreaks due to commercially distributed foods are rarely reported in the United States, and only 2 have been previously identified in Minnesota, both due to oysters. METHODS: In August 2016, we investigated an outbreak of norovirus gastroenteritis in Minnesota that was linked to consumption of commercially distributed ice cream at multiple venues. Sanitarians from local public health agencies visited the facilities involved for follow-up, and case-control studies were conducted. The outbreak was identified by linking multiple independent illness reports to a centralized foodborne illness complaint system and subsequently confirmed though genotyping of stool specimens. RESULTS: A total of 15 cases from 4 venues were reported. Raspberry chocolate chip ice cream was statistically associated with illness in 2 analytic studies (6 of 7 cases vs 0 of 7 controls; odds ratio, undefined; P = .005). Norovirus GII.17[P17] (GII.17 Kawasaki) strains from case stool specimens matched norovirus found in frozen raspberries imported from China that were used to make the implicated ice cream. CONCLUSIONS: To our knowledge, this is the first norovirus outbreak due to commercially distributed frozen berries identified in the United States. To detect norovirus outbreaks associated with commercially distributed food vehicles, investigators should thoroughly investigate all norovirus outbreaks (including stool testing and genotyping), coordinate complaint and response activities across agencies and jurisdictions, and consider testing food for norovirus when appropriate.

Moving Away from Population-Based Case-Control Studies during Outbreak Investigations.

Population-based case-control studies are a time- and labor-intensive component of foodborne outbreak investigations. One alternative is a binomial trial that asks the question "if the likelihood of each case's having eaten a given food is no different from that of the average person in the population, how often would we find, by chance alone, that x of n (or more) cases would have eaten this food?" Calculating a binomial trial requires background exposure data. We conducted case-control studies and binomial trials in two foodborne outbreaks and compared results. In both outbreaks, using binomial trials we found much less than a 5% probability that the number of cases eating the suspected food vehicle would have occurred by chance. These results were comparable with results of the case-control studies, but with considerably less effort. When background exposure data are available, binomial trials are an efficient way to explore hypotheses that can be further tested by traceback efforts to identify a common source.

Multistate Outbreak of Salmonella Anatum Infections Linked to Imported Hot Peppers - United States, May-July 2016.

Foodborne salmonellosis causes an estimated 1 million illnesses and 400 deaths annually in the United States (1). Salmonella Anatum is one of the top 20 Salmonella serotypes in the United States. During 2013-2015 there were approximately 300-350 annual illnesses reported to PulseNet, the national molecular subtyping network for foodborne disease surveillance. In June 2016, PulseNet identified a cluster of 16 Salmonella Anatum infections with an indistinguishable pulsed-field gel electrophoresis (PFGE) pattern from four states.* In April 2016, the same PFGE pattern had been uploaded to PulseNet from an isolate obtained from an Anaheim pepper, a mild to medium hot pepper. Hot peppers include many pepper varieties, such as Anaheim, jalapeño, poblano, and serrano, which can vary in heat level from mild to very hot depending on the variety and preparation. This rare PFGE pattern had been seen only 24 times previously in the PulseNet database, compared with common PFGE patterns for this serotype which have been seen in the database hundreds of times. Local and state health departments, CDC, and the Food and Drug Administration (FDA) investigated to determine the cause of the outbreak. Thirty-two patients in nine states were identified with illness onsets from May 6-July 9, 2016. Whole-genome sequencing (WGS) was performed to characterize clinical isolates and the Anaheim pepper isolate further. The combined evidence indicated that fresh hot peppers were the likely source of infection; however, a single pepper type or source farm was not identified. This outbreak highlights challenges in reconciling epidemiologic and WGS data, and the difficulties of identifying ingredient-level exposures through epidemiologic investigations alone.

Characteristics of Clusters of Salmonella and Escherichia coli O157 Detected by Pulsed-Field Gel Electrophoresis that Predict Identification of Outbreaks.

INTRODUCTION: Molecular subtyping of pathogens is critical for foodborne disease outbreak detection and investigation. Many clusters initially identified by pulsed-field gel electrophoresis (PFGE) are not confirmed as point-source outbreaks. We evaluated characteristics of clusters that can help prioritize investigations to maximize effective use of limited resources. MATERIALS AND METHODS: A multiagency collaboration (FoodNet) collected data on Salmonella and Escherichia coli O157 clusters for 3 years. Cluster size, timing, extent, and nature of epidemiologic investigations were analyzed to determine associations with whether the cluster was identified as a confirmed outbreak. RESULTS: During the 3-year study period, 948 PFGE clusters were identified; 849 (90%) were Salmonella and 99 (10%) were E. coli O157. Of those, 192 (20%) were ultimately identified as outbreaks (154 [18%] of Salmonella and 38 [38%] of E. coli O157 clusters). Successful investigation was significantly associated with larger cluster size, more rapid submission of isolates (e.g., for Salmonella, 6 days for outbreaks vs. 8 days for nonoutbreaks) and PFGE result reporting to investigators (16 days vs. 29 days, respectively), and performance of analytic studies (completed in 33% of Salmonella outbreaks vs. 1% of nonoutbreaks) and environmental investigations (40% and 1%, respectively). Intervals between first and second cases in a cluster did not differ significantly between outbreaks and nonoutbreaks. CONCLUSIONS: Molecular subtyping of pathogens is a rapidly advancing technology, and successfully identifying outbreaks will vary by pathogen and methods used. Understanding criteria for successfully investigating outbreaks is critical for efficiently using limited resources.

Incidence of Cronobacter spp. infections, United States, 2003-2009.

During 2003-2009, we identified 544 cases of Cronobacter spp. infection from 6 US states. The highest percentage of invasive infections occurred among children <5 years of age; urine isolates predominated among adults. Rates of invasive infections among infants approximate earlier estimates. Overall incidence of 0.66 cases/100,000 population was higher than anticipated.

Travel-associated enteric infections diagnosed after return to the United States, Foodborne Diseases Active Surveillance Network (FoodNet), 2004-2009.

BACKGROUND: Approximately 40% of US travelers to less developed countries experience diarrheal illness. Using data from the Foodborne Diseases Active Surveillance Network (FoodNet), we describe travel-associated enteric infections during 2004-2009, characterizing the patients, pathogens, and destinations involved. METHODS: FoodNet conducts active surveillance at 10 US sites for laboratory-confirmed infections with 9 pathogens transmitted commonly through food. Travel-associated infections are infections diagnosed in the United States but likely acquired abroad based on a pathogen-specific time window between return from international travel to diagnosis. We compare the demographic, clinical, and exposure-related characteristics of travelers with those of nontravelers and estimate the risk of travel-associated infections by destination, using US Department of Commerce data. RESULTS: Of 64,039 enteric infections reported to FoodNet with information about travel, 8270 (13%) were travel associated. The pathogens identified most commonly in travelers were Campylobacter (42%), nontyphoidal Salmonella (32%), and Shigella (13%). The most common travel destinations were Mexico, India, Peru, Dominican Republic, and Jamaica. Most travel-associated infections occurred in travelers returning from Latin America and the Caribbean (LAC). Risk was greatest after travel to Africa (75.9 cases per 100,000 population), followed by Asia (22.7 cases per 100,000), and LAC (20.0 cases per 100,000). CONCLUSIONS: The Latin America and Caribbean region accounts for most travel-associated enteric infections diagnosed in the United States, although travel to Africa carries the greatest risk. Although FoodNet surveillance does not cover enterotoxigenic Escherichia coli, a common travel-associated infection, this information about other key enteric pathogens can be used by travelers and clinicians in pre- and posttravel consultations.

Non-O157 Shiga toxin-producing Escherichia coli associated with venison.

We investigated an outbreak of non-O157 Shiga toxin-producing Escherichia coli at a high school in Minnesota, USA, in November 2010. Consuming undercooked venison and not washing hands after handling raw venison were associated with illness. E. coli O103:H2 and non-Shiga toxin-producing E. coli O145:NM were isolated from ill students and venison.

Use of traceback methods to confirm the source of a multistate Escherichia coli O157:H7 outbreak due to in-shell hazelnuts.

Traceback methods by state regulatory agencies were used to complement traditional epidemiological cluster investigation methods and confirmed hazelnuts (also referred to as filberts) as the vehicle in a multistate outbreak of Escherichia coli O157:H7 infections. Bulk in-shell hazelnut and mixed-nut purchase locations were identified during the initial epidemiological interviews. Based on purchase dates and case onset dates, regulators in Minnesota, Michigan, and Wisconsin traced product back through the supply chain. Six (86%) retail locations received the suspect hazelnut or mixed-nut shipments from a Minnesota distributor, with one retailer (14%) receiving products from a Wisconsin distributor. Both distributors received 100% of their bulk in-shell hazelnuts and mixed nuts from a distributor in California. The California distributor received 99% of their hazelnuts from a packing company in Oregon. The California distributor received the hazelnuts in 50-lb (22.7-kg) bags and either resold them without opening the bags or used the in-shell hazelnuts in the manufacture of their in-shell mixed nuts. Records at the packing company in Oregon were incomplete or lacked sufficient detail needed to identify a suspect farm or group of suspect farms. Laboratory samples collected from human cases and subsequently recalled product matched the outbreak pulsed-field gel electrophoresis subtype of E. coli O157:H7. Hazelnut harvesting practices create a plausible route of contamination from fecal matter from domestic ruminants or wild deer. This outbreak investigation demonstrates the use of product traceback data to rapidly test an epidemiological hypothesis.

Salmonella enterica pulsed-field gel electrophoresis clusters, Minnesota, USA, 2001-2007.

We determined characteristics of Salmonella enterica pulsed-field gel electrophoresis clusters that predict their being solved (i.e., that result in identification of a confirmed outbreak). Clusters were investigated by the Minnesota Department of Health by using a dynamic iterative model. During 2001-2007, a total of 43 (12.5%) of 344 clusters were solved. Clusters of ≥4 isolates were more likely to be solved than clusters of 2 isolates. Clusters in which the first 3 case isolates were received at the Minnesota Department of Health within 7 days were more likely to be solved than were clusters in which the first 3 case isolates were received over a period >14 days. If resources do not permit investigation of all S. enterica pulsed-field gel electrophoresis clusters, investigation of clusters of ≥4 cases and clusters in which the first 3 case isolates were received at a public health laboratory within 7 days may improve outbreak investigations.