National Outbreak Reporting System Research Articles

Missingness and algorithmic bias: an example from the United States National Outbreak Reporting System, 2009-2019.

Growing debates about algorithmic bias in public health surveillance lack specific examples. We tested a common assumption that exposure and illness periods coincide and demonstrated how algorithmic bias can arise due to missingness of critical information related to illness and exposure durations. We examined 9407 outbreaks recorded by the United States National Outbreak Reporting System (NORS) from January 1, 2009 through December 31, 2019 and detected algorithmic bias, a systematic over- or under-estimation of foodborne disease outbreak (FBDO) durations due to missing start and end dates. For 7037 (75%) FBDOs with complete date-time information, ~ 60% reported that the exposure period ended before the illness period started. For 2079 (87.7%) FBDOs with missing exposure dates, average illness durations were ~ 5.3 times longer (p < 0.001) than those with complete information, prompting the potential for algorithmic bias. Modern surveillance systems must be equipped with investigative capacities to examine and assess structural data missingness that can lead to bias.

Surveillance of Waterborne Disease Outbreaks Associated with Drinking Water - United States, 2015-2020.

Public health agencies in U.S. states, territories, and freely associated states investigate and voluntarily report waterborne disease outbreaks to CDC through the National Outbreak Reporting System (NORS). This report summarizes NORS drinking water outbreak epidemiologic, laboratory, and environmental data, including data for both public and private drinking water systems. The report presents outbreak-contributing factors (i.e., practices and factors that lead to outbreaks) and, for the first time, categorizes outbreaks as biofilm pathogen or enteric illness associated. 2015-2020. CDC launched NORS in 2009 as a web-based platform into which public health departments voluntarily enter outbreak information. Through NORS, CDC collects reports of enteric disease outbreaks caused by bacterial, viral, parasitic, chemical, toxin, and unknown agents as well as foodborne and waterborne outbreaks of nonenteric disease. Data provided by NORS users, when known, for drinking water outbreaks include 1) the number of cases, hospitalizations, and deaths; 2) the etiologic agent (confirmed or suspected); 3) the implicated type of water system (e.g., community or individual or private); 4) the setting of exposure (e.g., hospital or health care facility; hotel, motel, lodge, or inn; or private residence); and 5) relevant epidemiologic and environmental data needed to describe the outbreak and characterize contributing factors. During 2015-2020, public health officials from 28 states voluntarily reported 214 outbreaks associated with drinking water and 454 contributing factor types. The reported etiologies included 187 (87%) biofilm associated, 24 (11%) enteric illness associated, two (1%) unknown, and one (<1%) chemical or toxin. A total of 172 (80%) outbreaks were linked to water from public water systems, 22 (10%) to unknown water systems, 17 (8%) to individual or private systems, and two (0.9%) to other systems; one (0.5%) system type was not reported. Drinking water-associated outbreaks resulted in at least 2,140 cases of illness, 563 hospitalizations (26% of cases), and 88 deaths (4% of cases). Individual or private water systems were implicated in 944 (43%) cases, 52 (9%) hospitalizations, and 14 (16%) deaths.Enteric illness-associated pathogens were implicated in 1,299 (61%) of all illnesses, and 10 (2%) hospitalizations. No deaths were reported. Among these illnesses, three pathogens (norovirus, Shigella, and Campylobacter) or multiple etiologies including these pathogens resulted in 1,225 (94%) cases. The drinking water source was identified most often (n = 34; 7%) as the contributing factor in enteric disease outbreaks. When water source (e.g., groundwater) was known (n = 14), wells were identified in 13 (93%) of enteric disease outbreaks.Most biofilm-related outbreak reports implicated Legionella (n = 184; 98%); two nontuberculous mycobacteria (NTM) (1%) and one Pseudomonas (0.5%) outbreaks comprised the remaining. Legionella-associated outbreaks generally increased over the study period (14 in 2015, 31 in 2016, 30 in 2017, 34 in 2018, 33 in 2019, and 18 in 2020). The Legionella-associated outbreaks resulted in 786 (37%) of all illnesses, 544 (97%) hospitalizations, and 86 (98%) of all deaths. Legionella also was the outbreak etiology in 160 (92%) public water system outbreaks. Outbreak reports cited the premise or point of use location most frequently as the contributing factor for Legionella and other biofilm-associated pathogen outbreaks (n = 287; 63%). Legionella was reported to NORS in 2015 and 2019 as the cause of three outbreaks in private residences (2). The observed range of biofilm and enteric drinking water pathogen contributing factors illustrate the complexity of drinking water-related disease prevention and the need for water source-to-tap prevention strategies. Legionella-associated outbreaks have increased in number over time and were the leading cause of reported drinking water outbreaks, including hospitalizations and deaths. Enteric illness outbreaks primarily linked to wells represented approximately half the cases during this reporting period. This report enhances CDC efforts to estimate the U.S. illness and health care cost impacts of waterborne disease, which revealed that biofilm-related pathogens, NTM, and Legionella have emerged as the predominant causes of hospitalizations and deaths from waterborne- and drinking water-associated disease. Public health departments, regulators, and drinking water partners can use these findings to identify emerging waterborne disease threats, guide outbreak response and prevention programs, and support drinking water regulatory efforts.

The genomic and epidemiological virulence patterns of Salmonella enterica serovars in the United States.

The serovars of Salmonella enterica display dramatic differences in pathogenesis and host preferences. We developed a process (patent pending) for grouping Salmonella isolates and serovars by their public health risk. We collated a curated set of 12,337 S. enterica isolate genomes from human, beef, and bovine sources in the US. After annotating a virulence gene catalog for each isolate, we used unsupervised random forest methods to estimate the proximity (similarity) between isolates based upon the genomic presentation of putative virulence traits We then grouped isolates (virulence clusters) using hierarchical clustering (Ward's method), used non-parametric bootstrapping to assess cluster stability, and externally validated the clusters against epidemiological virulence measures from FoodNet, the National Outbreak Reporting System (NORS), and US federal sampling of beef products. We identified five stable virulence clusters of S. enterica serovars. Cluster 1 (higher virulence) serovars yielded an annual incidence rate of domestically acquired sporadic cases roughly one and a half times higher than the other four clusters combined (Clusters 2-5, lower virulence). Compared to other clusters, cluster 1 also had a higher proportion of infections leading to hospitalization and was implicated in more foodborne and beef-associated outbreaks, despite being isolated at a similar frequency from beef products as other clusters. We also identified subpopulations within 11 serovars. Remarkably, we found S. Infantis and S. Typhimurium subpopulations that significantly differed in genome length and clinical case presentation. Further, we found that the presence of the pESI plasmid accounted for the genome length differences between the S. Infantis subpopulations. Our results show that S. enterica strains associated with highest incidence of human infections share a common virulence repertoire. This work could be updated regularly and used in combination with foodborne surveillance information to prioritize serovars of public health concern.

P29-011-23 Structural Missingness and Algorithmic Bias in Supply Chain Stage and Food Product Records of Foodborne Disease Outbreaks: The National Outbreak Reporting System, 2009-2019

P29-011-23 Structural Missingness and Algorithmic Bias in Supply Chain Stage and Food Product Records of Foodborne Disease Outbreaks: The National Outbreak Reporting System, 2009-2019

Foodborne Illness Outbreaks at Retail Food Establishments - National Environmental Assessment Reporting System, 25 State and Local Health Departments, 2017-2019.

Each year, state and local public health departments report hundreds of foodborne illness outbreaks associated with retail food establishments (e.g., restaurants or caterers) to CDC. Typically, investigations involve epidemiology, laboratory, and environmental health components. Health departments voluntarily report epidemiologic and laboratory data from their foodborne illness outbreak investigations to CDC through the National Outbreak Reporting System (NORS); however, minimal environmental health data from outbreak investigations are reported to NORS. This report summarizes environmental health data collected during outbreak investigations and reported to the National Environmental Assessment Reporting System (NEARS). 2017-2019. In 2014, CDC launched NEARS to complement NORS surveillance and to use these data to enhance prevention efforts. State and local health departments voluntarily enter data from their foodborne illness outbreak investigations of retail food establishments into NEARS. These data include characteristics of foodborne illness outbreaks (e.g., etiologic agent and factors contributing to the outbreak), characteristics of establishments with outbreaks (e.g., number of meals served daily), and food safety policies in these establishments (e.g., ill worker policy requirements). NEARS is the only available data source that collects environmental characteristics of retail establishments with foodborne illness outbreaks. During 2017-2019, a total of 800 foodborne illness outbreaks associated with 875 retail food establishments were reported to NEARS by 25 state and local health departments. Among outbreaks with a confirmed or suspected agent (555 of 800 [69.4%]), the most common pathogens were norovirus and Salmonella, accounting for 47.0% and 18.6% of outbreaks, respectively. Contributing factors were identified in 62.5% of outbreaks. Approximately 40% of outbreaks with identified contributing factors had at least one reported factor associated with food contamination by an ill or infectious food worker. Investigators conducted an interview with an establishment manager in 679 (84.9%) outbreaks. Of the 725 managers interviewed, most (91.7%) said their establishment had a policy requiring food workers to notify their manager when they were ill, and 66.0% also said these policies were written. Only 23.0% said their policy listed all five illness symptoms workers needed to notify managers about (i.e., vomiting, diarrhea, jaundice, sore throat with fever, and lesion with pus). Most (85.5%) said that their establishment had a policy restricting or excluding ill workers from working, and 62.4% said these policies were written. Only 17.8% said their policy listed all five illness symptoms that would require restriction or exclusion from work. Only 16.1% of establishments with outbreaks had policies addressing all four components relating to ill or infectious workers (i.e., policy requires workers to notify a manager when they are ill, policy specifies all five illness symptoms workers need to notify managers about, policy restricts or excludes ill workers from working, and policy specifies all five illness symptoms requiring restriction or exclusion from work). Norovirus was the most commonly identified cause of outbreaks reported to NEARS, and contamination of food by ill or infectious food workers contributed to approximately 40% of outbreaks with identified contributing factors. These findings are consistent with findings from other national outbreak data sets and highlight the role of ill workers in foodborne illness outbreaks. Although a majority of managers reported their establishment had an ill worker policy, often these policies were missing components intended to reduce foodborne illness risk. Contamination of food by ill or infectious food workers is an important cause of outbreaks; therefore, the content and enforcement of existing policies might need to be re-examined and refined. Retail food establishments can reduce viral foodborne illness outbreaks by protecting food from contamination through proper hand hygiene and excluding ill or infectious workers from working. Development and implementation of policies that prevent contamination of food by workers are important to foodborne outbreak reduction. NEARS data can help identify gaps in food safety policies and practices, particularly those concerning ill workers. Future analyses of stratified data linking specific outbreak agents and foods with outbreak contributing factors can help guide the development of effective prevention approaches by describing how establishments' characteristics and food safety policies and practices relate to foodborne illness outbreaks.

Characteristics associated with successful foodborne outbreak investigations involving United States retail food establishments (2014-2016).

This study examined relationships between foodborne outbreak investigation characteristics, such as the epidemiological methods used, and the success of the investigation, as determined by whether the investigation identified an outbreak agent (i.e. pathogen), food item and contributing factor. This study used data from the Centers for Disease Control and Prevention's (CDC) National Outbreak Reporting System and National Environmental Assessment Reporting System to identify outbreak investigation characteristics associated with outbreak investigation success. We identified investigation characteristics that increase the probability of successful outbreak investigations: a rigorous epidemiology investigation method; a thorough environmental assessment, as measured by number of visits to complete the assessment; and the collection of clinical samples. This research highlights the importance of a comprehensive outbreak investigation, which includes epidemiology, environmental health and laboratory personnel working together to solve the outbreak.

Childcare and School Acute Gastroenteritis Outbreaks: 2009-2020.

Acute gastroenteritis (AGE) outbreaks commonly occur in congregate settings, including schools and childcare facilities. These outbreaks disrupt institutions, causing absences and temporary facility closures. This study analyzed the epidemiology of school and childcare AGE outbreaks in the United States. We analyzed AGE outbreaks occurring in kindergarten to grade 12 schools and childcare facilities reported via the National Outbreak Reporting System in the United States from 2009 to 2019 and compared this information to 2020 data. Outbreak and case characteristics were compared using the Kruskal-Wallis rank sum test, χ2 goodness-of-fit test, and Fisher exact test. From 2009 to 2019, there were 2623 school, 1972 childcare, and 38 school and childcare outbreaks. School outbreaks were larger (median, 29 cases) than childcare outbreaks (median, 10 cases). Childcare outbreaks were longer (median, 15 days) than school outbreaks (median, 9 days). Norovirus (2383 outbreaks; 110 190 illnesses) and Shigella spp. (756 outbreaks; 9123 illnesses) were the most reported etiologies. Norovirus was the leading etiology in schools; norovirus and Shigella spp. were dominant etiologies in childcare centers. Most (85.7%) outbreaks were spread via person-to-person contact. In 2020, 123 outbreaks were reported, 85% in the first quarter. Schools and childcare centers are common AGE outbreak settings in the United States. Most outbreaks were caused by norovirus and Shigella spp. and spread via person-to-person transmission. Fewer outbreaks were reported in 2020 from the COVID-19 pandemic. Prevention and control efforts should focus on interrupting transmission, including environmental disinfection, proper handwashing, safe diapering, and exclusion of ill persons.

Spatiotemporal Trends in Norovirus Outbreaks in the United States, 2009-2019.

Globally, noroviruses cause infections year-round but have recognized winter seasonality in the Northern Hemisphere and yearly variations in incidence. With candidate norovirus vaccines in development, understanding temporal and geographic trends in norovirus disease is important to inform potential vaccination strategies and evaluate vaccine impact. We analyzed data from the National Outbreak Reporting System (NORS) and CaliciNet on single-state norovirus outbreaks that occurred during August 2009-July 2019 in the contiguous United States. We defined norovirus season onset and offset as the weeks by which 10% and 90% of norovirus outbreaks in a surveillance year occurred, respectively, and duration as the difference in weeks between onset and offset. We compared norovirus seasons across surveillance years and geographic regions. During August 2009-July 2019, 24 995 single-state norovirus outbreaks were reported to NORS and/or CaliciNet. Nationally, the median norovirus season duration was 24 weeks, with onset occurring between October and December and offset occurring between April and May. Across all years combined, we observed a west-to-east trend in seasonality, with the earliest onset (October) and latest offset (May) occurring in western regions and the latest onset (December) and earliest offset (April) occurring in northeastern regions. Timing and duration of the US norovirus season varied annually but generally occurred during October-May. Norovirus wintertime seasonality was less distinct in western regions and was progressively more pronounced moving east. Further understanding the drivers of spatiotemporal dynamics of norovirus could provide insights into factors that promote virus transmission and help guide future interventions.

Foodborne Illness Outbreak Severity Across Geographic and Supply Chain Contamination Locations in the United States, 2009–2019

ObjectivesIn 2009, the Centers for Disease Control and Prevention's National Outbreak Reporting System (NORS) began collecting supply chain contamination data as part of foodborne outbreak (FBO) traceback investigations. We created an integrated FBO severity score measure and examined differences in FBO severity by geographic and supply chain contamination locations. We used 9,407 NORS records between 2009–2019 to demonstrate the utility of the proposed methodology.MethodsThe severity scores were composed of 11 metrics based on outbreak intensity and duration characteristics and metrics’ completeness. Metrics were normalized (with natural log-transformation), calibrated (to 0–1 scale), and weighed (by completeness) across all recorded outbreaks. Individual outbreak scores ranged from 0 (lowest severity) to 1 (highest severity). We compared averages of severity scores across geographic (i.e., multistate and single state exposure outbreak) and supply chain contamination locations (i.e., suspected or confirmed before preparation, preparation, unknown and missing) using tobit-regression models.ResultsAll FBOs reported the state of exposure; 5,500 (58.5%) reported supply chain contamination location. Multistate exposure FBOs had higher median severity scores than single state outbreaks (0.54 [0.44, 0.67] vs 0.28 [0.16, 0.41], P < 0.001). FBOs with reported point of contamination that occurred before preparation had higher median severity scores than all other stages (0.36 [0.27, 0.49] vs 0.26 [0.15, 0.41], 0.25 [0.13, 0.39], and 0.29 [0.16, 0.43], P < 0.001, for preparation, unknown and missing stages respectively).ConclusionsUnderstanding an FBO's severity by geographic and supply chain contamination location helps to quantify supply chain vulnerability and improve monitoring of food safety. Identification of supply chain contamination at high level granularity and completeness is critical for developing foodborne outbreak (FBO) prediction analytics aimed to reduce both the volume and severity of outbreaks and illnesses.Funding SourcesDoD, ODNI, NIFA, NSF, USIAD.

Exploring Risk Factors of Recall-Associated Foodborne Disease Outbreaks in the United States, 2009-2019.

Earlier identification and removal of contaminated food products is crucial in reducing economic burdens of foodborne outbreaks. Recalls are a safety measure that is deployed to prevent foodborne illnesses. However, few studies have examined temporal trends in recalls or compared risk factors between non-recall and recall outbreaks in the United States, due to disparate and often incomplete surveillance records in publicly reported data. We demonstrated the usability of the electronic Foodborne Outbreak Reporting System (eFORS) and National Outbreak Reporting System (NORS) for describing temporal trends and outbreak risk factors of food recalls in 1998–2019. We examined monthly trends between surveillance systems by using segmented time-series analyses. We compared the risk factors (e.g., multistate outbreak, contamination supply chain stage, pathogen etiology, and food products) of recalls and non-recalls by using logistic regression models. Out of 22,972 outbreaks, 305 (1.3%) resulted in recalls and 9378 (41%) had missing recall information. However, outbreaks with missing recall information decreased at an accelerating rate of ~25%/month in 2004–2009 and at a decelerating rate of ~13%/month after the transition from eFORS to NORS in 2009–2019. Irrespective of the contaminant etiology, multistate outbreaks according to the residence of ill persons had odds 11.00–13.50 times (7.00, 21.60) that of single-state outbreaks resulting in a recall (p < 0.001) when controlling for all risk factors. Electronic reporting has improved the availability of food recall data, yet retrospective investigations of historical records are needed. The investigation of recalls enhances public health professionals’ understanding of their annual financial burden and improves outbreak prediction analytics to reduce the likelihood and severity of recalls.

Evaluating Completeness of Foodborne Outbreak Reporting in the United States, 1998-2019.

Public health agencies routinely collect time-referenced records to describe and compare foodborne outbreak characteristics. Few studies provide comprehensive metadata to inform researchers of data limitations prior to conducting statistical modeling. We described the completeness of 103 variables for 22,792 outbreaks publicly reported by the United States Centers for Disease Control and Prevention’s (US CDC’s) electronic Foodborne Outbreak Reporting System (eFORS) and National Outbreak Reporting System (NORS). We compared monthly trends of completeness during eFORS (1998–2008) and NORS (2009–2019) reporting periods using segmented time series analyses adjusted for seasonality. We quantified the overall, annual, and monthly completeness as the percentage of outbreaks with blank records per our study period, calendar year, and study month, respectively. We found that outbreaks of unknown genus (n = 7401), Norovirus (n = 6414), Salmonella (n = 2872), Clostridium (n = 944), and multiple genera (n = 779) accounted for 80.77% of all outbreaks. However, crude completeness ranged from 46.06% to 60.19% across the 103 variables assessed. Variables with the lowest crude completeness (ranging 3.32–6.98%) included pathogen, specimen etiological testing, and secondary transmission traceback information. Variables with low (<35%) average monthly completeness during eFORS increased by 0.33–0.40%/month after transitioning to NORS, most likely due to the expansion of surveillance capacity and coverage within the new reporting system. Examining completeness metrics in outbreak surveillance systems provides essential information on the availability of data for public reuse. These metadata offer important insights for public health statisticians and modelers to precisely monitor and track the geographic spread, event duration, and illness intensity of foodborne outbreaks.

Analysing foodborne illness outbreak severity in the USA, 2009–19

BackgroundIn the USA, one in six Americans have had a foodborne illness, resulting in approximately US$17·6 billion (2018) of losses annually attributed to medical costs, productivity losses, and economic burden due to death. Previous research has characterised these burdens with use of various methods, including disability-adjusted life-years (DALYs), medical care costs, and revenue losses of food retailers. However, these indices assess only the socioeconomic burdens of outbreaks without providing an index to compare the health-related severity of outbreaks regarding geographical spread of transmission, outbreak duration, and the morbidity and mortality of case outcomes. MethodsIn this study, we proposed a data-driven index for evaluating outbreak severity using the publicly available US Centers for Disease Control and Prevention's National Outbreak Reporting System (NORS) database from Jan 1, 2009, to Dec 31, 2019. We identified 67 metrics related to the geographical extent (eg, counties or states where individuals with a foodborne illness resided and were exposed), case severity (eg, primary cases, hospital admissions, emergency room visits, and deaths), duration (eg, days of illness and days of exposure events), and their ratios. We selected 11 metrics to create the index on the basis of completeness and distributional characteristics of these metrics. We generated index scores by normalising natural log-transformed values on a 0–1 scale and averaging all metrics per outbreak. Scores ranged from 0 (lowest severity) to 1 (highest severity). FindingsNORS reported 9407 outbreaks in our 11-year study period. We found that bacterial outbreaks associated with the genera Streptococcus, Listeria, and Salmonella had the highest median severity scores, whereas Bacillus, Staphylococcus, and Clostridium had the lowest scores. Among protozoa, Cryptosporidium and Cyclospora had the lowest median scores, whereas Giardia and Toxoplasma had the highest scores. Hepatitis had the highest median score for virus-associated outbreaks, whereas Norovirus, which had the most outbreaks reported in our study period (n=3088), had the lowest score. InterpretationOur index illustrates the usefulness of publicly reported surveillance data in establishing a data-driven approach for monitoring the severity of foodborne outbreaks regarding their spread, duration, and morbidity and mortality. Differences in outbreak severity by pathogen inform how to best allocate resources for monitoring, tracking, and preventing foodborne disease outbreaks. Being data driven, our index emphasises the importance of improved data quality, integrity, and completeness of surveillance records. Future research should strive to validate this index by use of longitudinal cohort studies. FundingUS Department of Defense, National Institute of Food and Agriculture.

Norovirus Outbreaks in Long-term Care Facilities in the United States, 2009-2018: A Decade of Surveillance.

In the United States, norovirus is the leading cause of healthcare-associated gastroenteritis outbreaks. To inform prevention efforts, we describe the epidemiology of norovirus outbreaks in long-term care facilities (LTCFs). The Centers for Disease Control and Prevention (CDC) collect epidemiologic and laboratory data on norovirus outbreaks from US health departments through the National Outbreak Reporting System (NORS) and CaliciNet. Reports from both systems were merged, and norovirus outbreaks in nursing homes, assisted living, and other LTCFs occurring in 2009-2018 were analyzed. Data from the Centers for Medicare and Medicaid Services and the National Center for Health Statistics were used to estimate state LTCF counts. During 2009-2018, 50 states, Washington D.C., and Puerto Rico reported 13 092 norovirus outbreaks and 416 284 outbreak-associated cases in LTCFs. Participation in NORS and CaliciNet increased from 2009 to 2014 and median reporting of LTCF norovirus outbreaks stabilized at 4.1 outbreaks per 100 LTCFs (interquartile range [IQR]: 1.0-7.1) annually since 2014. Most outbreaks were spread via person-to-person transmission (90.4%), and 75% occurred during December-March. Genogroup was reported for 7292 outbreaks with 862 (11.8%) positive for GI and 6370 (87.3%) for GII. Among 4425 GII outbreaks with typing data, 3618 (81.8%) were GII.4. LTCF residents had higher attack rates than staff (median 29.0% vs 10.9%; P < .001). For every 1000 cases, there were 21.6 hospitalizations and 2.3 deaths. LTCFs have a high burden of norovirus outbreaks. Most LTCF norovirus outbreaks occurred during winter months and were spread person-to-person. Outbreak surveillance can inform development of interventions for this vulnerable population, such as vaccines targeting GII.4 norovirus strains.

Enteric Illness Outbreaks Reported Through the National Outbreak Reporting System-United States, 2009-2019.

The National Outbreak Reporting System (NORS) captures data on foodborne, waterborne, and enteric illness outbreaks in the United States. This study describes enteric illness outbreaks reported during 11 years of surveillance. We extracted finalized reports from NORS for outbreaks occurring during 2009-2019. Outbreaks were included if caused by an enteric etiology or if any patients reported diarrhea, vomiting, bloody stools, or unspecified acute gastroenteritis. A total of 38 395 outbreaks met inclusion criteria, increasing from 1932 in 2009 to 3889 in 2019. Outbreaks were most commonly transmitted through person-to-person contact (n = 23 812; 62%) and contaminated food (n = 9234; 24%). Norovirus was the most commonly reported etiology, reported in 22 820 (59%) outbreaks, followed by Salmonella (n = 2449; 6%) and Shigella (n = 1171; 3%). Norovirus outbreaks were significantly larger, with a median of 22 illnesses per outbreak, than outbreaks caused by the other most common outbreak etiologies (P < .0001, all comparisons). Hospitalization rates were higher in outbreaks caused by Salmonella and Escherichia coli outbreaks (20.9% and 22.8%, respectively) than those caused by norovirus (2%). Case fatality rate was highest in E. coli outbreaks (0.5%) and lowest in Shigella and Campylobacter outbreaks (0.02%). Norovirus caused the most outbreaks and outbreak-associated illness, hospitalizations, and deaths. However, persons in E. coli and Salmonella outbreaks were more likely to be hospitalized or die. Outbreak surveillance through NORS provides the relative contributions of each mode of transmission and etiology for reported enteric illness outbreaks, which can guide targeted interventions.

The correlation between Google trends and salmonellosis

BackgroundSalmonella infection (salmonellosis) is a common infectious disease leading to gastroenteritis, dehydration, uveitis, etc. Internet search is a new method to monitor the outbreak of infectious disease. An internet-based surveillance system using internet data is logistically advantageous and economical to show term-related diseases. In this study, we tried to determine the relationship between salmonellosis and Google Trends in the USA from January 2004 to December 2017.MethodsWe downloaded the reported salmonellosis in the USA from the National Outbreak Reporting System (NORS) from January 2004 to December 2017. Additionally, we downloaded the Google search terms related to salmonellosis from Google Trends in the same period. Cross-correlation analysis and multiple regression analysis were conducted.ResultsThe results showed that 6 Google Trends search terms appeared earlier than reported salmonellosis, 26 Google Trends search terms coincided with salmonellosis, and 16 Google Trends search terms appeared after salmonellosis were reported. When the search terms preceded outbreaks, “foods” (t = 2.927, P = 0.004) was a predictor of salmonellosis. When the search terms coincided with outbreaks, “hotel” (t = 1.854, P = 0.066), “poor sanitation” (t = 2.895, P = 0.004), “blueberries” (t = 2.441, P = 0.016), and “hypovolemic shock” (t = 2.001, P = 0.047) were predictors of salmonellosis. When the search terms appeared after outbreaks, “ice cream” (t = 3.077, P = 0.002) was the predictor of salmonellosis. Finally, we identified the most important indicators of Google Trends search terms, including “hotel” (t = 1.854, P = 0.066), “poor sanitation” (t = 2.895, P = 0.004), “blueberries” (t = 2.441, P = 0.016), and “hypovolemic shock” (t = 2.001, P = 0.047). In the future, the increased search activities of these terms might indicate the salmonellosis.ConclusionWe evaluated the related Google Trends search terms with salmonellosis and identified the most important predictors of salmonellosis outbreak.

Impact of Nonpharmaceutical Interventions for Severe Acute Respiratory Syndrome Coronavirus 2 on Norovirus Outbreaks: An Analysis of Outbreaks Reported By 9 US States.

In April 2020, the incidence of norovirus outbreaks reported to the National Outbreak Reporting System (NORS) dramatically declined. We used regression models to determine if this decline was best explained by underreporting, seasonal trends, or reduced exposure due to non-pharmaceutical interventions (NPIs) implemented for SARS-CoV-2 using data from 9 states from July 2012–July 2020. The decline in norovirus outbreaks was significant for all 9 states and underreporting or seasonality are unlikely to be the primary explanations for these findings. These patterns were similar across a variety of settings. NPIs appear to have reduced incidence of norovirus, a non-respiratory pathogen.

Non-Norovirus Viral Gastroenteritis Outbreaks Reported to the National Outbreak Reporting System, USA, 2009-2018.

During 2009–2018, four adenovirus, 10 astrovirus, 123 rotavirus, and 107 sapovirus gastroenteritis outbreaks were reported to the US National Outbreak Reporting System (annual median 30 outbreaks). Most were attributable to person-to-person transmission in long-term care facilities, daycares, and schools. Investigations of norovirus-negative gastroenteritis outbreaks should include testing for these viruses.

Characterizing Norovirus Transmission from Outbreak Data, United States.

Norovirus is the leading cause of acute gastroenteritis outbreaks in the United States. We estimated the basic (R0) and effective (Re) reproduction numbers for 7,094 norovirus outbreaks reported to the National Outbreak Reporting System (NORS) during 2009–2017 and used regression models to assess whether transmission varied by outbreak setting. The median R0 was 2.75 (interquartile range [IQR] 2.38–3.65), and median Re was 1.29 (IQR 1.12–1.74). Long-term care and assisted living facilities had an R0 of 3.35 (95% CI 3.26–3.45), but R0 did not differ substantially for outbreaks in other settings, except for outbreaks in schools, colleges, and universities, which had an R0 of 2.92 (95% CI 2.82–3.03). Seasonally, R0 was lowest (3.11 [95% CI 2.97–3.25]) in summer and peaked in fall and winter. Overall, we saw little variability in transmission across different outbreaks settings in the United States.

Outbreaks Associated with Untreated Recreational Water - California, Maine, and Minnesota, 2018-2019.

Outbreaks associated with fresh or marine (i.e., untreated) recreational water can be caused by pathogens or chemicals, including toxins. Voluntary reporting of these outbreaks to CDC's National Outbreak Reporting System (NORS) began in 2009. NORS data for 2009-2017 are finalized, and data for 2018-2019 are provisional. During 2009-2019 (as of May 13, 2020), public health officials from 31 states voluntarily reported 119 untreated recreational water-associated outbreaks, resulting at least 5,240 cases; 103 of the outbreaks (87%) started during June-August. Among the 119 outbreaks, 88 (74%) had confirmed etiologies. The leading etiologies were enteric pathogens: norovirus (19 [22%] outbreaks; 1,858 cases); Shiga toxin-producing Escherichia coli (STEC) (19 [22%]; 240), Cryptosporidium (17 [19%]; 237), and Shigella (14 [16%]; 713). This report highlights three examples of outbreaks that occurred during 2018-2019, were caused by leading etiologies (Shigella, norovirus, or STEC), and demonstrate the wide geographic distribution of such outbreaks across the United States. Detection and investigation of untreated recreational water-associated outbreaks are challenging, and the sources of these outbreaks often are not identified. Tools for controlling and preventing transmission of enteric pathogens through untreated recreational water include epidemiologic investigations, regular monitoring of water quality (i.e., testing for fecal indicator bacteria), microbial source tracking, and health policy and communications (e.g., observing beach closure signs and not swimming while ill with diarrhea).

Cryptosporidiosis outbreaks — United States, 2009–2017

Cryptosporidium is a parasite that causes cryptosporidiosis, a profuse, watery diarrhea that can last up to 3 weeks in immunocompetent patients and can lead to life-threatening malnutrition and wasting in immunocompromised patients.* Fecal-oral transmission can occur by ingestion of contaminated recreational water, drinking water, or food, or through contact with infected persons or animals. For the period 2009-2017, public health officials from 40 states and Puerto Rico voluntarily reported 444 cryptosporidiosis outbreaks resulting in 7,465 cases. Exposure to treated recreational water (e.g., in pools and water playgrounds) was associated with 156 (35.1%) outbreaks resulting in 4,232 (56.7%) cases. Other predominant outbreak exposures included contact with cattle (65 outbreaks; 14.6%) and contact with infected persons in child care settings (57; 12.8%). The annual number of reported cryptosporidiosis outbreaks overall increased an average of approximately 13% per year over time. Reversing this trend will require dissemination of prevention messages to discourage swimming or attending child care while ill with diarrhea and encourage hand washing after contact with animals. Prevention and control measures can be optimized by improving understanding of Cryptosporidium transmission through regular analysis of systematically collected epidemiologic and molecular characterization data.