Reported Incidence of Infections Caused by Pathogens Transmitted Commonly Through Food: Impact of Increased Use of Culture-Independent Diagnostic Tests - Foodborne Diseases Active Surveillance Network, 1996-2023.

Reducing foodborne disease incidence is a public health priority. This report summarizes preliminary 2023 Foodborne Diseases Active Surveillance Network (FoodNet) data and highlights efforts to increase the representativeness of FoodNet. During 2023, incidences of domestically acquired campylobacteriosis, Shiga toxin-producing Escherichia coli infection, yersiniosis, vibriosis, and cyclosporiasis increased, whereas those of listeriosis, salmonellosis, and shigellosis remained stable compared with incidences during 2016-2018, the baseline used for tracking progress towards federal disease reduction goals. During 2023, the incidence and percentage of infections diagnosed by culture-independent diagnostic tests (CIDTs) reported to FoodNet continued to increase, and the percentage of cases that yielded an isolate decreased, affecting observed trends in incidence. Because CIDTs allow for diagnosis of infections that previously would have gone undetected, lack of progress toward disease reduction goals might reflect changing diagnostic practices rather than an actual increase in incidence. Continued surveillance is needed to monitor the impact of changing diagnostic practices on disease trends, and targeted prevention efforts are needed to meet disease reduction goals. During 2023, FoodNet expanded its catchment area for the first time since 2004. This expansion improved the representativeness of the FoodNet catchment area, the ability of FoodNet to monitor trends in disease incidence, and the generalizability of FoodNet data.

Investigating the relationship between extreme weather and cryptosporidiosis and giardiasis in Colorado: A multi-decade study using distributed-lag nonlinear models.

Environmentally-mediated protozoan diseases like cryptosporidiosis and giardiasis are likely to be highly impacted by extreme weather, as climate-related conditions like temperature and precipitation have been linked to their survival, distribution, and overall transmission success. Our aim was to investigate the relationship between extreme temperature and precipitation and cryptosporidiosis and giardiasis infection using monthly weather data and case reports from Colorado counties over a twenty-one year period. Data on reportable diseases and weather among Colorado counties were collected using the Colorado Electronic Disease Reporting System (CEDRS) and the Daily Surface Weather and Climatological Summaries (Daymet) Version 3 dataset, respectively. We used a conditional Poisson distributed-lag nonlinear modeling approach to estimate the lagged association (between 0 and 12-months) between relative temperature and precipitation extremes and the risk of cryptosporidiosis and giardiasis infection in Colorado counties between 1997 and 2017, relative to the risk found at average values of temperature and precipitation for a given county and month. We found distinctly different patterns in the associations between temperature extremes and cryptosporidiosis, versus temperature extremes and giardiasis. When maximum or minimum temperatures were high (90th percentile) or very high (95th percentile), we found a significant increase in cryptosporidiosis risk, but a significant decrease in giardiasis risk, relative to risk at the county and calendar-month mean. Conversely, we found very similar relationships between precipitation extremes and both cryptosporidiosis and giardiasis, which highlighted the prominent role of long-term (>8 months) lags. Our study presents novel insights on the influence that extreme temperature and precipitation can have on parasitic disease transmission in real-world settings. Additionally, we present preliminary evidence that the standard lag periods that are typically used in epidemiological studies to assess the impacts of extreme weather on cryptosporidiosis and giardiasis may not be capturing the entire relevant period.

Lessons Learned From a Sequential Mixed-Mode Survey Design to Recruit and Collect Data From Case-Control Study Participants: Formative Evaluation.

BACKGROUND: Sequential mixed-mode surveys using both web-based surveys and telephone interviews are increasingly being used in observational studies and have been shown to have many benefits; however, the application of this survey design has not been evaluated in the context of epidemiological case-control studies. OBJECTIVE: In this paper, we discuss the challenges, benefits, and limitations of using a sequential mixed-mode survey design for a case-control study assessing risk factors during the COVID-19 pandemic. METHODS: Colorado adults testing positive for SARS-CoV-2 were randomly selected and matched to those with a negative SARS-CoV-2 test result from March to April 2021. Participants were first contacted by SMS text message to complete a self-administered web-based survey asking about community exposures and behaviors. Those who did not respond were contacted for a telephone interview. We evaluated the representativeness of survey participants to sample populations and compared sociodemographic characteristics, participant responses, and time and resource requirements by survey mode using descriptive statistics and logistic regression models. RESULTS: Of enrolled case and control participants, most were interviewed by telephone (308/537, 57.4% and 342/648, 52.8%, respectively), with overall enrollment more than doubling after interviewers called nonresponders. Participants identifying as female or White non-Hispanic, residing in urban areas, and not working outside the home were more likely to complete the web-based survey. Telephone participants were more likely than web-based participants to be aged 18-39 years or 60 years and older and reside in areas with lower levels of education, more linguistic isolation, lower income, and more people of color. While there were statistically significant sociodemographic differences noted between web-based and telephone case and control participants and their respective sample pools, participants were more similar to sample pools when web-based and telephone responses were combined. Web-based participants were less likely to report close contact with an individual with COVID-19 (odds ratio [OR] 0.70, 95% CI 0.53-0.94) but more likely to report community exposures, including visiting a grocery store or retail shop (OR 1.55, 95% CI 1.13-2.12), restaurant or cafe or coffee shop (OR 1.52, 95% CI 1.20-1.92), attending a gathering (OR 1.69, 95% CI 1.34-2.15), or sport or sporting event (OR 1.05, 95% CI 1.05-1.88). The web-based survey required an average of 0.03 (SD 0) person-hours per enrolled participant and US $920 in resources, whereas the telephone interview required an average of 5.11 person-hours per enrolled participant and US $70,000 in interviewer wages. CONCLUSIONS: While we still encountered control recruitment challenges noted in other observational studies, the sequential mixed-mode design was an efficient method for recruiting a more representative group of participants for a case-control study with limited impact on data quality and should be considered during public health emergencies when timely and accurate exposure information is needed to inform control measures.

Exploring the association of weather variability on Campylobacter - A systematic review.

BACKGROUND: Previous work has found climate change-induced weather variability is suspected to increase the transmission of enteric pathogens, including Campylobacter, a leading cause of bacterial gastroenteritis. While the relationship between extreme weather events and diarrheal diseases has been documented, the specific impact on Campylobacter infections remains underexplored. OBJECTIVE: To synthesize the peer-reviewed literature exploring the effect of weather variability on Campylobacter infections in humans. METHODS: The review included English language, peer-reviewed articles, published up to September 1, 2022 in PubMed, Embase, GEOBASE, Agriculture and Environmental Science Database, and CABI Global Health exploring the effect of an antecedent weather event on human enteric illness caused by Campylobacter (PROSPERO Protocol # 351884). We extracted study information including data sources, methods, summary measures, and effect sizes. Quality and weight of evidence reported was summarized and bias assessed for each article. RESULTS: After screening 278 articles, 47 articles (34 studies, 13 outbreak reports) were included in the evidence synthesis. Antecedent weather events included precipitation (n = 35), temperature (n = 30), relative humidity (n = 7), sunshine (n = 6), and El Niño and La Niña (n = 3). Reviewed studies demonstrated that increases in precipitation and temperature were correlated with Campylobacter infections under specific conditions, whereas low relative humidity and sunshine were negatively correlated. Articles estimating the effect of animal operations (n = 15) found presence and density of animal operations were significantly associated with infections. However, most of the included articles did not assess confounding by seasonality, presence of animal operations, or describe estimates of risk. DISCUSSION: This review explores what is known about the influence of weather events on Campylobacter and identifies previously underreported negative associations between low relative humidity and sunshine on Campylobacter infections. Future research should explore pathogen-specific estimates of risk, which can be used to influence public health strategies, improve source attribution and causal pathways, and project disease burden due to climate change.

Improving occupational health surveillance for enteric infections.

AIMS: Enteric pathogens with a livestock reservoir pose a unique risk to people in occupations with regular contact with animals. However, public health surveillance of occupational exposures is inadequate, with surveillance for occupation typically focusing on the risk of transmission and the need for worker exclusion, rather than workplace exposures. To improve surveillance for occupational zoonoses, the Colorado Integrated Food Safety Center of Excellence convened a group of subject matter experts who developed a set of variables on occupation, industry, and exposures, which were integrated into Colorado's surveillance system in 2017. We evaluated the quality and completeness of these new occupational fields for interviewed cases with laboratory-confirmed zoonotic infections and compared occupations to cases with a non-zoonotic infection (Shigella) and to employment data from the Bureau of Labor Statistics. METHODS AND RESULTS: From March 2017 through December 2019, 3668 domestically acquired, laboratory-confirmed sporadic infections of Campylobacter, Cryptosporidium, Shiga toxin-producing Escherichia coli, and non-typhoidal Salmonella among individuals ≥14 years of age were interviewed by public health. We found asking explicitly about occupational exposure risks and focusing on animal exposures, improved data quality and accuracy. Of the cases who stated that they were employed, 262 (13%) reported working in an occupation with regular animal exposure, and 254 (14%) reported an industry with regular animal exposure. Cases with an animal exposure occupation were more likely to be male and live in a rural or frontier county compared to other occupations. All occupations with regular animal contact were reported at a higher frequency than among Shigella cases or the general population. CONCLUSIONS: Public health efforts, both in occupational health and communicable disease sectors, should be made to improve surveillance for enteric zoonoses and identify opportunities for prevention strategies.

Laboratory Criteria for Exclusion and Readmission of Potentially Infectious Persons in Sensitive Settings in the Age of Culture-Independent Diagnostic Tests: Report of a Multidisciplinary Workgroup.

Culture-independent diagnostic tests (CIDTs) are increasingly used for clinical diagnosis of gastrointestinal diseases such as salmonellosis, Shiga toxin-producing E. coli disease, and shigellosis because of their speed, convenience, and generally high-performance characteristics. These tests are also used to screen potentially infectious asymptomatic persons during outbreak investigations in sensitive settings such as childcare, food service, and healthcare. However, only limited performance data are available for CIDTs used on specimens from asymptomatic persons. The Association of Public Health Laboratories (APHL) and Council of State and Territorial Epidemiologists (CSTE) convened a workgroup to examine the available scientific data to inform interim decision-making related to exclusion and readmission criteria for potentially infectious persons in sensitive settings, the risks and benefits of different testing strategies, and to identify knowledge gaps for further research. This is the report on the Workgroup findings.

Multistate Outbreak of Salmonella Thompson Infections Linked to Seafood Exposure - United States, 2021.

In July 2021, the Colorado Department of Public Health and Environment (CDPHE) laboratory identified a cluster of five Salmonella enterica serotype Thompson isolates related to one another within one allele difference, using whole genome multilocus sequence typing (wgMLST). These five isolates, submitted to the public health laboratory as is routine process for confirmatory testing of Salmonella, were highly related to those identified in a 2020 multistate investigation, during which traceback was conducted for sushi-grade tuna and salmon; a common supplier was not identified. The 2021 investigation commenced on August 5, 2021, with five patients living in Colorado, and one each in Missouri, Washington, and Wisconsin. During August-December 2021, CDC, CDPHE, public health and regulatory officials in several states, and the Food and Drug Administration (FDA) conducted epidemiologic, environmental, and laboratory investigations of this multistate outbreak of Salmonella Thompson. Isolates were genetically related to one another and to 2020 isolates within zero to one allele difference. Implicated seafood products were traced to a single seafood distributor, in which the outbreak strain was identified through environmental sampling, and in which inspection identified inadequate sanitization and opportunities for cross-contamination of raw fish. The distributor issued a voluntary recall of 16 seafood items with high potential for contamination and completed remediation actions. This outbreak illustrated the importance of effective cleaning and sanitizing procedures and implementation of controls. When multiple products are recalled during an outbreak investigation, collaboration between public health agencies and implicated facilities can help provide food safety information to restaurants, retailers, and consumers, and to ensure disposal of all recalled products.

Community exposures among Colorado adults who tested positive for SARS-CoV-2 -A case-control study, March-December 2021.

OBJECTIVES: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, which causes coronavirus disease 2019 (COVID-19), is spread primarily through exposure to respiratory droplets from close contact with an infected person. To inform prevention measures, we conducted a case-control study among Colorado adults to assess the risk of SARS-CoV-2 infection from community exposures. METHODS: Cases were symptomatic Colorado adults (aged ≥18 years) with a positive SARS-CoV-2 test by reverse transcription-polymerase chain reaction (RT-PCR) reported to Colorado's COVID-19 surveillance system. From March 16 to December 23, 2021, cases were randomly selected from surveillance data ≤12 days after their specimen collection date. Cases were matched on age, zip code (urban areas) or region (rural/frontier areas), and specimen collection date with controls randomly selected among persons with a reported negative SARS-CoV-2 test result. Data on close contact and community exposures were obtained from surveillance and a survey administered online. RESULTS: The most common exposure locations among all cases and controls were place of employment, social events, or gatherings and the most frequently reported exposure relationship was co-worker or friend. Cases were more likely than controls to work outside the home (adjusted odds ratio (aOR) 1.18, 95% confidence interval (CI): 1.09-1.28) in industries and occupations related to accommodation and food services, retail sales, and construction. Cases were also more likely than controls to report contact with a non-household member with confirmed or suspected COVID-19 (aOR 1.16, 95% CI: 1.06-1.27). CONCLUSIONS: Understanding the settings and activities associated with a higher risk of SARS-CoV-2 infection is essential for informing prevention measures aimed at reducing the transmission of SARS-CoV-2 and other respiratory diseases. These findings emphasize the risk of community exposure to infected persons and the need for workplace precautions in preventing ongoing transmission.

Evaluation of Correctional Facility COVID-19 Outbreaks With Layered Mitigation Strategies Including Vaccination: Colorado, 2020-2021.

In 2020-2021, a Colorado corrections facility experienced four COVID-19 outbreaks. Case counts, attack rates (ARs) in people who are detained or incarcerated (PDI), and mitigation measures used in each outbreak were compared to evaluate effects of combined strategies. Serial PCR testing, isolation/quarantine, and masking were implemented in outbreak 1. Daily staff antigen testing began in outbreak 2. Facility-wide COVID-19 vaccination started in outbreak 3 and coverage increased by the end of outbreak 4 (PDI: <1% to 59%, staff: 27% to 40%). Despite detection of variants of concern, outbreaks 3 and 4 had 97% lower PDI ARs (both 1%) than outbreak 2 (29%). Daily staff testing and increasing vaccination coverage, with other outbreak mitigation strategies, are important to reduce COVID-19 transmission in congregate settings.

Preliminary Incidence and Trends of Infections Caused by Pathogens Transmitted Commonly Through Food - Foodborne Diseases Active Surveillance Network, 10 U.S. Sites, 2016-2021.

To evaluate progress toward prevention of enteric infections in the United States, the Foodborne Diseases Active Surveillance Network (FoodNet) conducts active population-based surveillance for laboratory-diagnosed infections caused by Campylobacter, Cyclospora, Listeria, Salmonella, Shiga toxin-producing Escherichia coli (STEC), Shigella, Vibrio, and Yersinia at 10 U.S. sites. This report summarizes preliminary 2021 data and describes changes in annual incidence compared with the average annual incidence for 2016-2018, the reference period for the U.S. Department of Health and Human Services' (HHS) Healthy People 2030 goals for some pathogens (1). During 2021, the incidence of infections caused by Salmonella decreased, incidence of infections caused by Cyclospora, Yersinia, and Vibrio increased, and incidence of infections caused by other pathogens did not change. As in 2020, behavioral modifications and public health interventions implemented to control the COVID-19 pandemic might have decreased transmission of enteric infections (2). Other factors (e.g., increased use of telemedicine and continued increase in use of culture-independent diagnostic tests [CIDTs]) might have altered their detection or reporting (2). Much work remains to achieve HHS Healthy People 2030 goals, particularly for Salmonella infections, which are frequently attributed to poultry products and produce, and Campylobacter infections, which are frequently attributed to chicken products (3).

Outbreak of Foodborne Botulism Associated with a Commercially Produced Multipack Potato Product, Colorado: September 2019.

During September 2019, public health authorities in El Paso County, Colorado, were notified of four patients who had presented to nearby hospitals with clinical features consistent with botulism, a paralytic illness caused by botulinum neurotoxin. One patient died soon after presentation; the other three patients required intensive care but recovered after receiving botulism antitoxin. Botulinum toxin type A was detected in serum from all patients. On further investigation, all four patients had shared a meal that included commercially prepared roasted potatoes from an individual package without refrigeration instructions that had been left unrefrigerated for 15 d. Storage of the product at ambient temperature likely allowed botulism spores to produce botulinum toxin, resulting in severe illness and death. The manufacturer improved labeling in response to this outbreak. Public health officials should consider unrefrigerated potato products as a potential source of botulism; clinicians should consider botulism as a possible cause of paralytic illness.

Using Online Surveys for Enteric Disease Case Investigations: A Pilot Project.

Typically conducted by telephone, routine enteric disease case interviews are critical for foodborne illness surveillance, outbreak detection, and disease control. However, an increasing case load, along with the increased use of mobile telephones, has made case interviews more challenging to complete. For this reason, the Colorado Integrated Food Safety Center of Excellence developed and evaluated a pilot program using online surveys to supplement routine telephone-based enteric disease case investigations. From April to September 2019, investigators offered laboratory-confirmed Giardia cases from three Colorado counties the option of either a telephone interview or an online survey. The paper-based Giardia case investigation form was mapped to an online survey in Research Electronic Data Capture. We evaluated the pilot project response rates, timeliness, data quality, demographics, and user feedback. Of the 32 Giardia cases contacted, 66% requested the online survey, and of these, 81% completed the survey. Online survey cases were slightly younger (median: 42 vs. 48 years) and the majority agreed that the survey was easy to use (93%), did not take too much time (87%), and was easy to understand (67%). Staff time decreased for online surveys compared with telephone interviews (median: 6 vs. 19 min); however, the time from case report to interview completion doubled (median: 4 vs. 2 d for telephone interview cases) and data quality decreased slightly. Given limited public health agency resources, supplementing telephone interviews with online surveys may increase the efficiency of routine enteric case investigations. The results of this pilot project indicate online surveys are popular with enteric disease cases and substantially reduce staff time. Methods to improve the timeliness and data quality of online surveys should be explored to reduce the impact on disease control and outbreak detection activities.

Coronavirus Disease among Workers in Food Processing, Food Manufacturing, and Agriculture Workplaces.

We describe coronavirus disease (COVID-19) among US food manufacturing and agriculture workers and provide updated information on meat and poultry processing workers. Among 742 food and agriculture workplaces in 30 states, 8,978 workers had confirmed COVID-19; 55 workers died. Racial and ethnic minority workers could be disproportionately affected by COVID-19.

Update: COVID-19 Among Workers in Meat and Poultry Processing Facilities - United States, April-May 2020.

Meat and poultry processing facilities face distinctive challenges in the control of infectious diseases, including coronavirus disease 2019 (COVID-19) (1). COVID-19 outbreaks among meat and poultry processing facility workers can rapidly affect large numbers of persons. Assessment of COVID-19 cases among workers in 115 meat and poultry processing facilities through April 27, 2020, documented 4,913 cases and 20 deaths reported by 19 states (1). This report provides updated aggregate data from states regarding the number of meat and poultry processing facilities affected by COVID-19, the number and demographic characteristics of affected workers, and the number of COVID-19-associated deaths among workers, as well as descriptions of interventions and prevention efforts at these facilities. Aggregate data on confirmed COVID-19 cases and deaths among workers identified and reported through May 31, 2020, were obtained from 239 affected facilities (those with a laboratory-confirmed COVID-19 case in one or more workers) in 23 states.* COVID-19 was confirmed in 16,233 workers, including 86 COVID-19-related deaths. Among 14 states reporting the total number of workers in affected meat and poultry processing facilities (112,616), COVID-19 was diagnosed in 9.1% of workers. Among 9,919 (61%) cases in 21 states with reported race/ethnicity, 87% occurred among racial and ethnic minority workers. Commonly reported interventions and prevention efforts at facilities included implementing worker temperature or symptom screening and COVID-19 education, mandating face coverings, adding hand hygiene stations, and adding physical barriers between workers. Targeted workplace interventions and prevention efforts that are appropriately tailored to the groups most affected by COVID-19 are critical to reducing both COVID-19-associated occupational risk and health disparities among vulnerable populations. Implementation of these interventions and prevention efforts† across meat and poultry processing facilities nationally could help protect workers in this critical infrastructure industry.

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.

Outbreak of hepatitis A in the USA associated with frozen pomegranate arils imported from Turkey: an epidemiological case study.

BACKGROUND: In May, 2013, an outbreak of symptomatic hepatitis A virus infections occurred in the USA. Federal, state, and local public health officials investigated the cause of the outbreak and instituted actions to control its spread. We investigated the source of the outbreak and assessed the public health measures used. METHODS: We interviewed patients, obtained their shopping information, and did genetic analysis of hepatitis A virus recovered from patients' serum and stool samples. We tested products for the virus and traced supply chains. FINDINGS: Of 165 patients identified from ten states, 69 (42%) were admitted to hospital, two developed fulminant hepatitis, and one needed a liver transplant; none died. Illness onset occurred from March 31 to Aug 12, 2013. The median age of patients was 47 years (IQR 35-58) and 91 (55%) were women. 153 patients (93%) reported consuming product B from retailer A. 40 patients (24%) had product B in their freezers, and 113 (68%) bought it according to data from retailer A. Hepatitis A virus genotype IB, uncommon in the Americas, was recovered from specimens from 117 people with hepatitis A virus illness. Pomegranate arils that were imported from Turkey--where genotype IB is common--were identified in product B. No hepatitis A virus was detected in product B. INTERPRETATION: Imported frozen pomegranate arils were identified as the vehicle early in the investigation by combining epidemiology--with data from several sources--genetic analysis of patient samples, and product tracing. Product B was removed from store shelves, the public were warned not to eat product B, product recalls took place, and postexposure prophylaxis with both hepatitis A virus vaccine and immunoglobulin was provided. Our findings show that modern public health actions can help rapidly detect and control hepatitis A virus illness caused by imported food. Our findings show that postexposure prophylaxis can successfully prevent hepatitis A illness when a specific product is identified. Imported food products combined with waning immunity in some adult populations might make this type of intervention necessary in the future. FUNDING: US Centers for Disease Control and Prevention, US Food and Drug Administration, and US state and local public health departments.