National Outbreak Reporting System Research Articles

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.

Emerging Novel GII.P16 Noroviruses Associated with Multiple Capsid Genotypes.

Noroviruses evolve by antigenic drift and recombination, which occurs most frequently at the junction between the non-structural and structural protein coding genomic regions. In 2015, a novel GII.P16-GII.4 Sydney recombinant strain emerged, replacing the predominance of GII.Pe-GII.4 Sydney among US outbreaks. Distinct from GII.P16 polymerases detected since 2010, this novel GII.P16 was subsequently detected among GII.1, GII.2, GII.3, GII.10 and GII.12 viruses, prompting an investigation on the unique characteristics of these viruses. Norovirus positive samples (n = 1807) were dual-typed, of which a subset (n = 124) was sequenced to yield near-complete genomes. CaliciNet and National Outbreak Reporting System (NORS) records were matched to link outbreak characteristics and case outcomes to molecular data and GenBank was mined for contextualization. Recombination with the novel GII.P16 polymerase extended GII.4 Sydney predominance and increased the number of GII.2 outbreaks in the US. Introduction of the novel GII.P16 noroviruses occurred without unique amino acid changes in VP1, more severe case outcomes, or differences in affected population. However, unique changes were found among NS1/2, NS4 and VP2 proteins, which have immune antagonistic functions, and the RdRp. Multiple polymerase-capsid combinations were detected among GII viruses including 11 involving GII.P16. Molecular surveillance of protein sequences from norovirus genomes can inform the functional importance of amino acid changes in emerging recombinant viruses and aid in vaccine and antiviral formulation.

Norovirus outbreaks on college and university campuses

Objective: To describe norovirus outbreaks at colleges and universities. Participants: None. Conducted September 2016 to March 2018. Methods: College and university norovirus outbreaks reported to the US National Outbreak Reporting System (NORS, 2009–2016) or published and indexed by EMBASE, PubMed, and Web of Science (1985–2017) were analyzed. Results: Seventy-seven norovirus outbreaks were reported to NORS and 23 were identified in the systematic literature review. Outbreaks occurred more frequently during the beginning of the school year (September–February). NORS outbreaks were more often spread by person-to-person transmission (61%) and, in published outbreaks, by food (57%). The reported exposures of published outbreaks were campus dining (n = 8) and ill food service workers (n = 7). Higher attack rates were associated with smaller on-campus population size, social networks or residences, and specific food exposures. Common control measures were communal area disinfection and health/hygiene education. Conclusions: Recommendations summarized to prevent and control norovirus outbreaks at colleges or universities.

Outbreaks of Salmonella enterica infections linked to animal contact: Demographic and outbreak characteristics and comparison to foodborne outbreaks-United States, 2009-2014.

In the United States, multistate Salmonella outbreaks are most commonly linked to a food source; however, contact with live animals can also result in outbreaks of human illness. To characterize Salmonella outbreaks linked to animal contact and examine differences compared to foodborne outbreaks, we analysed data reported to the Centers for Disease Control and Prevention through the National Outbreak Reporting System (NORS) from 2009 to 2014 with a primary mode of transmission listed as "animal contact" or "food." Four hundred and eighty-four outbreaks with animal contact or foodborne transmission were reported through NORS; of these outbreaks, 99 (20.5%) resulted from Salmonella transmission through animal contact and 385 (79.5%) resulted from foodborne transmission, which resulted in 3,604 (19.8%) and 13,568 (80.2%) illnesses, respectively. A higher proportion of illnesses among children aged <1year and children aged 1-4years were linked to animal contact outbreaks compared to foodborne outbreaks (15.2% vs. 1.4%, p<0.01 and 24.5% vs. 5.6%, p<0.01, respectively). Illnesses resulting in hospitalizations (OR: 1.81, 95% CI: 1.62, 2.02) were more likely to be associated with animal contact compared to food. Animal contact outbreaks reported to NORS were more likely to be multistate compared to foodborne outbreaks (OR: 5.43, 95% CI: 3.37, 8.76) and had a longer median duration (99.0days vs. 9.0days, p<0.01). Characterizing the differences between outbreaks of illness linked to animal contact and outbreaks linked to food provides useful information to investigators to improve public health response.

The Norovirus Epidemiologic Triad: Predictors of Severe Outcomes in US Norovirus Outbreaks, 2009-2016.

Noroviruses are the leading cause of acute gastroenteritis outbreaks worldwide. Clarifying the viral, host, and environmental factors (epidemiologic triad) associated with severe outcomes can help target public health interventions. Acute norovirus outbreaks reported to the National Outbreak Reporting System (NORS) in 2009-2016 were linked to laboratory-confirmed norovirus outbreaks reported to CaliciNet. Outbreaks were analyzed for differences in genotype (GII.4 vs non-GII.4), hospitalization, and mortality rates by timing, setting, transmission mode, demographics, clinical symptoms, and health outcomes. A total of 3747 norovirus outbreaks were matched from NORS and CaliciNet. Multivariable models showed that GII.4 outbreaks (n = 2353) were associated with healthcare settings (odds ratio [OR], 3.94 [95% confidence interval {CI}, 2.99-5.23]), winter months (November-April; 1.55 [95% CI, 1.24-1.93]), and older age of cases (≥50% aged ≥75 years; 1.37 [95% CI, 1.04-1.79]). Severe outcomes were more likely among GII.4 outbreaks (hospitalization rate ratio [RR], 1.54 [95% CI, 1.23-1.96]; mortality RR, 2.77 [95% CI, 1.04-5.78]). Outbreaks in healthcare settings were also associated with higher hospitalization (RR, 3.22 [95% CI, 2.34-4.44]) and mortality rates (RR, 5.65 [95% CI, 1.92-18.70]). Severe outcomes more frequently occurred in norovirus outbreaks caused by GII.4 and those in healthcare settings. These results should help guide preventive interventions for targeted populations, including vaccine development.

Prevention and Control of Youth Camp-Associated Acute Gastroenteritis Outbreaks.

Approximately 14 million children attend more than 14000 US camps every year. Shared accommodations and activities can facilitate acute gastroenteritis (AGE) outbreaks. We analyzed data from the National Outbreak Reporting System on US youth camp-associated AGE outbreaks that occurred between 2009 and 2016. We also conducted a systematic literature search of youth camp-associated AGE outbreaks that have occurred around the world and a gray literature search for existing recommendations on outbreak prevention and control at camps worldwide. Thirty-nine US jurisdictions reported a total of 229 youth camp-associated AGE outbreaks to the National Outbreak Reporting System. Of the 226 outbreaks included in our analyses, 120 (53%) were reported to have resulted from person-to-person transmission, 42 (19%) from an unknown transmission mode, 38 (17%) from foodborne transmission, 19 (8%) from waterborne transmission, 5 (2%) from animal contact, and 2 (<1%) from environmental contamination. Among 170 (75%) outbreaks with a single suspected or confirmed etiology, norovirus (107 [63%] outbreaks), Salmonella spp (16 [9%]), and Shiga-toxin producing Escherichia coli (12 [7%]) were implicated most frequently. We identified 43 additional youth camp-associated AGE outbreaks in the literature that occurred in various countries between 1938 and 2014. Control measures identified through the literature search included camp closure, separation of ill campers, environmental disinfection, and education on food preparation and hand hygiene. Youth camp-associated AGE outbreaks are caused by numerous pathogens every year. These outbreaks are facilitated by factors that include improper food preparation, inadequate cleaning and disinfection, shared accommodations, and contact with animals. Health education focused on proper hygiene and preventing disease transmission could help control or prevent these outbreaks.

Surveillance for Foodborne Disease Outbreaks - United States, 2009-2015.

Problem/ConditionKnown foodborne disease agents are estimated to cause approximately 9.4 million illnesses each year in the United States. Although only a small subset of illnesses are associated with recognized outbreaks, data from outbreak investigations provide insight into the foods and pathogens that cause illnesses and the settings and conditions in which they occur.Reporting Period2009–2015Description of SystemThe Foodborne Disease Outbreak Surveillance System (FDOSS) collects data on foodborne disease outbreaks, which are defined as the occurrence of two or more cases of a similar illness resulting from the ingestion of a common food. Since the early 1960s, foodborne outbreaks have been reported voluntarily to CDC by state, local, and territorial health departments using a standard form. Beginning in 2009, FDOSS reporting was made through the National Outbreak Reporting System, a web-based platform launched that year.ResultsDuring 2009–2015, FDOSS received reports of 5,760 outbreaks that resulted in 100,939 illnesses, 5,699 hospitalizations, and 145 deaths. All 50 states, the District of Columbia, Puerto Rico, and CDC reported outbreaks. Among 2,953 outbreaks with a single confirmed etiology, norovirus was the most common cause of outbreaks (1,130 outbreaks [38%]) and outbreak-associated illnesses (27,623 illnesses [41%]), followed by Salmonella with 896 outbreaks (30%) and 23,662 illnesses (35%). Outbreaks caused by Listeria, Salmonella, and Shiga toxin-producing Escherichia coli (STEC) were responsible for 82% of all hospitalizations and 82% of deaths reported. Among 1,281 outbreaks in which the food reported could be classified into a single food category, fish were the most commonly implicated category (222 outbreaks [17%]), followed by dairy (136 [11%]) and chicken (123 [10%]). The food categories responsible for the most outbreak-associated illnesses were chicken (3,114 illnesses [12%]), pork (2,670 [10%]), and seeded vegetables (2,572 [10%]). Multistate outbreaks comprised only 3% of all outbreaks reported but accounted for 11% of illnesses, 34% of hospitalizations, and 54% of deaths.InterpretationFoodborne disease outbreaks provide information about the pathogens and foods responsible for illness. Norovirus remains the leading cause of foodborne disease outbreaks, highlighting the continued need for food safety improvements targeting worker health and hygiene in food service settings. Outbreaks caused by Listeria, Salmonella, and STEC are important targets for public health intervention efforts, and improving the safety of chicken, pork, and seeded vegetables should be a priority.Public Health ActionThe causes of foodborne illness should continue to be tracked and analyzed to inform disease prevention policies and initiatives. Strengthening the capacity of state and local health departments to investigate and report outbreaks will assist with these efforts through identification of the foods, etiologies, and settings linked to these outbreaks.

State-level adoption of national guidelines for norovirus outbreaks in health care settings

Clinical decision support (CDS) systems can help investigators use best practices when responding to outbreaks, but variation in guidelines between jurisdictions can make such systems hard to develop and implement. This study aimed to identify (1) the extent to which state-level guidelines adhere to national recommendations for norovirus outbreak response in health care settings and (2) the impact of variation between states on outbreak outcomes. State guidelines were obtained from Internet searches and direct contact with state public health officials in early 2016. Outcomes from norovirus outbreaks that occurred in 2015 were compared using data from the National Outbreak Reporting System. Guidelines were obtained from 41 of 45 (91%) state health departments that responded to queries or had guidelines available on their Web sites. Most state guidelines addressed each of the national recommendations, but specific guidance varied considerably. For example, among 36 states with guidance on numbers of stool specimens to collect, there were 21 different recommendations. Furthermore, having guidelines consistent with national recommendations was associated with fewer outbreaks reported and more outbreaks with confirmed etiology. This study identified substantial variation in state health care-associated norovirus outbreak response guidelines, which must be considered when developing related CDS systems. More research is needed to understand why this variation exists, how it impacts outbreak outcomes, and where improvements in evidence-based recommendations and communication of national guidance are needed.

Surveillance for Prevention &amp; Identification of GI Illness Outbreaks Associated with Swimming Pools

ObjectiveTo prevent and identify gastrointestinal outbreaks due to swimming pools using a two-part surveillance system i) Model Aquatic Health Code (MAHC) Guideline Survey and ii) syndromic surveillanceIntroductionSwimming in contaminated pools can cause gastroenteritis from water contaminated by viruses, bacteria, or parasites. Germs that cause gastroenteritis are shed in feces of infected persons, and easily spread to uninfected persons swimming in pools. Symptoms of gastrointestinal illness can include nausea, vomiting, watery or bloody diarrhea, and weight loss. Common causes of swimming-related gastroenteritis included viruses (norovirus), parasites (giardia, cryptosporidium), and bacteria (Escherichia coli, Shigella). Cryptosporidium is most common agent associated with swimming pool outbreaks. In 2011-2012, public health officials from 32 States reported 90 swimming-pool associated outbreaks to CDC’s Waterborne Disease and Outbreak Surveillance System (WBDOSS). These 90 outbreaks resulted in 1,788 cases, 95 hospitalizations, 1 death. 52% of these outbreaks were caused by Cryptosporidium.MethodsLiterature search was conducted using published peer-reviewed articles via PubMed and Internet websites including, CDC and U.S. consumer product safety commission, Agency for toxic substance and disease registry. Statistical data on GI illness outbreaks associated with swimming pools prevalence and outcomes were also reviewed. Current surveillance methods used for detecting prevalence of waterborne disease outbreaks are based on examples from Ohio and Nebraska to determine approaches and effectiveness of the systems.ResultsSurvey and Education Packet - Distribute a survey with questions about current MAHC guideline adherence and MAHC educational packets that include the incident response guidelines and the water contamination response logStrengths: Low cost, simple, and acceptableLimitations: Not timely event reportingEvent Reporting - Develop a website for reporting contamination events based on the water contamination response logStrengths: Timely reportingLimitations: Complex to setup and maintain, moderate cost, and may not be acceptablePool Inspections - Require pools to undergo periodic inspections to monitor adherence to MAHC guidelinesStrengths: Complete and representativeLimitations: Complex, expensive, not timely event reportingThe current system is based on state reporting to the CDC through the paper-based reporting waterborne disease outbreaks surveillance system (WBDOSS), and the National Outbreak Reporting System (NORS), an electronic reporting system in place since 2009CDC uses waterborne disease outbreak surveillance data too identify the types of etiologic agents, and settings associated with outbreakso evaluate the adequacy of regulations to promote healthy and safe swimmingo establish priorities to improve prevention, guidelines, and regulations at the local, state, and federal levelsThe WBDOSS is not sufficient to capture early detection and reporting of AGI outbreaks. We recommend the these surveillance approaches:Syndromic surveillance of WBD outbreaks to capture early outbreaks of diarrheal, and as many suspected cases as possible in a timely mannerSentinel surveillance at specific healthcare facilities in the proximity of swimming pools where outbreaks can occurActive Lab-based surveillance would offer more robust and complete analysis of the prevalence and incidence of acute GI illness outbreaks in the StateConclusionsOur study concluded that state health department should begin a two-part surveillance system: i) distributing MAHC guideline surveys &amp; education packet; ii) syndromic surveillance system for outbreaks. MAHC Guideline Survey and Education Packet would be cost effective to educate pool operators on current MAHC guidelines and gather baseline data on adherence to MAHC guidelines for responding to contamination events. Afterwards, once baseline data is gathered and awareness of the MAHC guidelines is established, the state health department can determine if event reporting or pool inspections are necessary to increase either the timeliness or representativeness of the surveillance system. Syndromic surveillance would be the most timely and sensitive surveillance system. This is important to achieve health department's goal of early outbreak detection. Both predictive value and data quality are limitations of syndromic surveillance system. Acute gastrointestinal illness is also caused by sources other than pool contamination which can cause false positives.References1-CDC. Protracted Outbreaks of Cryptosporidiosis Associated With Swimming Pool Use --- Ohio and Nebraska, 2000 MMWR 2001; 50(20); 406-410.http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5020a3.htm2-CDC. Outbreaks of Illness Associated with 2-Recreational Water — United States, 2011–2012 MMWR. 64(24); 668-672. http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6424a4.htm?s_cid=mm6424a4_w3-CDC. The Model Aquatic Health Code. August 2015. http://www.cdc.gov/mahc/index.htm4-CDC. (n.d.) Decoding the MAHC: The Model Aquatic Health Code. Retrieved from https://www.cdc.gov/healthywater/pdf/swimming/pools/mahc/decoding-the-mahc.pdf5-CDC. (2016). Fecal Incident Response Recommendations for Aquatic Staff. Retrieved from https://www.cdc.gov/healthywater/swimming/pdf/fecal-incident-response-guidelines.pdf6-CDC. (n.d.) Water Contamination Response Log. Retrieved from https://www.cdc.gov/healthywater/pdf/swimming/pools/water-contamination-response-log.pdf7-CDC. (2016). Model Aquatic Health Code Aquatic Facility Inspection Report. Retrieved from https://www.cdc.gov/mahc/pdf/mahc-aquatic-facility-inspection-report.pdf

Clinical and Epidemiologic Profiles for Identifying Norovirus in Acute Gastroenteritis Outbreak Investigations.

Noroviruses are the leading cause of acute gastroenteritis (AGE) outbreaks in the United States. However, outbreaks attributed to norovirus often lack confirmation by diagnostic testing. Clinical and epidemiologic profiles, such as the Kaplan criteria (vomiting in >50% cases, mean incubation period of 24-48 hours, mean duration of illness for 12-60 hours, and negative bacterial stool culture), have been used to distinguish norovirus outbreaks from those caused by bacteria. Kaplan criteria were evaluated among 10 023 outbreaks reported to the National Outbreak Reporting System (NORS) during 2009-2012. An alternate profile for distinguishing norovirus outbreaks from outbreaks caused by nonviral etiologies was identified using classification and regression tree (CART) modeling. Performance of the Kaplan criteria and alternate profile were compared among laboratory-confirmed outbreaks. The Kaplan criteria were 63.9% sensitive and 100% specific in discriminating norovirus from nonviral outbreaks, but only 3.3% of norovirus and 1.2% of nonviral outbreaks reported all criteria. Clinical and epidemiologic characteristics identified with CART modeling (ratio of proportion of cases with fever to the proportion of cases with vomiting <1, proportion of cases with bloody stool <0.1, proportion of cases with vomiting ≥0.26) were 85.7% sensitive and 92.4% specific for distinguishing norovirus from nonviral outbreaks and were applicable to more than 8 times as many outbreaks compared with the Kaplan criteria. Compared with the Kaplan criteria, the CART-derived profile had higher sensitivity and broader application in reported AGE outbreaks. Thus, this alternate profile may provide a more useful tool for identifying norovirus during outbreak investigations.

Epidemiology of Foodborne Norovirus Outbreaks - United States, 2009-2015.

Noroviruses are the leading cause of acute gastroenteritis and foodborne disease in the United States (U.S.). About 1 in 5 reported norovirus outbreaks are spread through foodborne transmission, presenting opportunities for prevention. We describe the epidemiology of U.S. foodborne norovirus outbreaks reported to national surveillance systems, including differences between genotypes. Foodborne outbreaks that occurred during August 2009-July 2015 with norovirus reported as a single confirmed etiology to the National Outbreak Reporting System (NORS) were matched with outbreaks reported to CaliciNet, a U.S. laboratory norovirus outbreak surveillance network. We analyzed these matched outbreaks stratified by genotype for epidemiologic characteristics, including setting, size and duration, health outcomes of case-patients, implicated food, and outbreak contributing factors. Four hundred ninety-three confirmed foodborne norovirus outbreaks were reported in both NORS and CaliciNet. The most common norovirus genotypes reported were GII.4 (52%), GII.6 (9%), and GI.3 (8%). Compared to non-GII.4 outbreaks, GII.4 outbreaks had higher hospitalization rates (12.8 vs. 4.8 per 1,000 cases, P < 0.01). While contaminated foods were identified and reported in only 35% of outbreaks, molluscan shellfish (4% overall) were more often implicated in non-GII.4 outbreaks than in GII.4 outbreaks (7% vs. 1%, P = 0.04). Of the 240 outbreaks reporting at least one contributing factor, food workers were implicated as the source of contamination in 182 (76%), with no difference between GII.4 and non-GII.4 (73% vs 79%, P = 0.3). Foodborne norovirus outbreaks are frequently reported in the U.S., most of which are caused by GII.4 noroviruses. Viruses of this genotype are associated with higher rates of hospitalization; non-GII.4 noroviruses are more frequently associated with contaminated molluscan shellfish. These surveillance data highlight the diversity of noroviruses causing foodborne disease and can help guide appropriate food safety interventions, including worker hygiene, improved food handling and preparation, and further development of norovirus vaccines.

Foodborne Illness Outbreak Investigation Training Needs: A Survey Among State Public Health Staff in the Northeast and Mid-Atlantic United States.

In 2011, the Food Safety and Modernization Act established Integrated Food Safety Centers of Excellence across the United States to train, educate, and enhance the skill of foodborne illness outbreak investigation teams. To target regional training efforts, the New York Integrated Food Safety Center of Excellence (NYCoE) identified training needs in food safety and foodborne illness investigations among public heath staff in 11 states and 1 large metropolitan area in the Northeast. To identify topics so as to develop training materials relevant to food safety and foodborne disease outbreaks in order to improve and impact foodborne outbreak investigations regionally and nationally. Cross-sectional, paper-based survey conducted in January-February 2016. Eleven Northeast and Mid-Atlantic states, and 1 large metropolitan area. Foodborne illness outbreak investigators in the NYCoE region. Identification of training needs, as self-reported by participants, regarding general foodborne outbreak investigation needs and those specific to epidemiologists, environmental health specialists, and laboratorians. Topics included basic food safety/processing knowledge, communication and metrics, and training formats. Information regarding demographics, utility of the NYCoE, and certificate programs was also collected. Surveys returned from 33 respondents (from 10 states and 1 metropolitan area) identified metrics (100%), increasing use of culture-independent diagnostic tests (85%), and guidance on implementation of the Council to Improve Foodborne Outbreak Response (guidelines (89%) as the top training needs. By field, epidemiologists cited training in applying whole genome sequencing (100%), environmental health specialists cited training on the National Outbreak Reporting System (67%), and laboratorians cited training on whole genome sequencing (91%) as important. Short, online, or in-person, 1- to 2-day trainings were the preferred training formats (≥91%). Respondents wanted certificate programs in food safety (73%). New diagnostic and molecular techniques are highly desirable topics for trainings, as is understanding national guidelines and outcome measures. Shorter and hands-on training formats, as well as certificate programs, are desirable. The NYCoE used the results of this survey to (i) select training topics for a Food Safety symposium conducted in July 2016 and to (ii) drive other activities.

Surveillance for Waterborne Disease Outbreaks Associated with Drinking Water - United States, 2013-2014.

Provision of safe water in the United States is vital to protecting public health (1). Public health agencies in the U.S. states and territories* report information on waterborne disease outbreaks to CDC through the National Outbreak Reporting System (NORS) (https://www.cdc.gov/healthywater/surveillance/index.html). During 2013-2014, 42 drinking water-associated† outbreaks were reported, accounting for at least 1,006 cases of illness, 124 hospitalizations, and 13 deaths. Legionella was associated with 57% of these outbreaks and all of the deaths. Sixty-nine percent of the reported illnesses occurred in four outbreaks in which the etiology was determined to be either a chemical or toxin or the parasite Cryptosporidium. Drinking water contamination events can cause disruptions in water service, large impacts on public health, and persistent community concern about drinking water quality. Effective water treatment and regulations can protect public drinking water supplies in the United States, and rapid detection, identification of the cause, and response to illness reports can reduce the transmission of infectious pathogens and harmful chemicals and toxins.

Waterborne Disease Outbreaks Associated With Environmental and Undetermined Exposures to Water - United States, 2013-2014.

Waterborne disease outbreaks in the United States are associated with a wide variety of water exposures and are reported annually to CDC on a voluntary basis by state and territorial health departments through the National Outbreak Reporting System (NORS). A majority of outbreaks arise from exposure to drinking water (1) or recreational water (2), whereas others are caused by an environmental exposure to water or an undetermined exposure to water. During 2013-2014, 15 outbreaks associated with an environmental exposure to water and 12 outbreaks with an undetermined exposure to water were reported, resulting in at least 289 cases of illness, 108 hospitalizations, and 17 deaths. Legionella was responsible for 63% of the outbreaks, 94% of hospitalizations, and all deaths. Outbreaks were also caused by Cryptosporidium, Pseudomonas, and Giardia, including six outbreaks of giardiasis caused by ingestion of water from a river, stream, or spring. Water management programs can effectively prevent outbreaks caused by environmental exposure to water from human-made water systems, while proper point-of-use treatment of water can prevent outbreaks caused by ingestion of water from natural water systems.

Increasing Campylobacter Infections, Outbreaks, and Antimicrobial Resistance in the United States, 2004-2012.

Campylobacteriosis, a leading cause of foodborne illness in the United States, was not nationally notifiable until 2015. Data describing national patterns and trends are limited. We describe the epidemiology of Campylobacter infections in the United States during 2004-2012. We summarized laboratory-confirmed campylobacteriosis data from the Nationally Notifiable Disease Surveillance System, National Outbreak Reporting System, National Antimicrobial Resistance Monitoring System, and Foodborne Diseases Active Surveillance Network. During 2004-2012, 303520 culture-confirmed campylobacteriosis cases were reported. Average annual incidence rate (IR) was 11.4 cases/100000 persons, with substantial variation by state (range, 3.1-47.6 cases/100000 persons). IRs among patients aged 0-4 years were more than double overall IRs. IRs were highest among males in all age groups. IRs in western states and rural counties were higher (16.2/100000 and 14.2/100000, respectively) than southern states and metropolitan counties (6.8/100000 and 11.0/100000, respectively). Annual IRs increased 21% from 10.5/100000 during 2004-2006 to 12.7/100000 during 2010-2012, with the greatest increases among persons aged >60 years (40%) and in southern states (32%). The annual median number of Campylobacter outbreaks increased from 28 in 2004-2006 to 56 in 2010-2012; in total, 347 were reported. Antimicrobial susceptibility testing of isolates from 4793 domestic and 1070 travel-associated infections revealed that, comparing 2004-2009 to 2010-2012, ciprofloxacin resistance increased among domestic infections (12.8% vs 16.1%). During 2004-2012, incidence of campylobacteriosis, outbreaks, and clinically significant antimicrobial resistance increased. Marked demographic and geographic differences exist. Our findings underscore the importance of national surveillance and understanding of risk factors to guide and target control measures.

Using Molecular Characterization to Support Investigations of Aquatic Facility-Associated Outbreaks of Cryptosporidiosis - Alabama, Arizona, and Ohio, 2016.

Cryptosporidiosis is a nationally notifiable gastrointestinal illness caused by parasitic protozoa of the genus Cryptosporidium, which can cause profuse, watery diarrhea that can last up to 2-3 weeks in immunocompetent patients and can lead to life-threatening wasting and malabsorption in immunocompromised patients. Fecal-oral transmission of Cryptosporidium oocysts, the parasite's infectious life stage, occurs via ingestion of contaminated recreational water, drinking water, or food, or following contact with infected persons or animals, particularly preweaned bovine calves (1). The typical incubation period is 2-10 days. Since 2004, the annual incidence of nationally notified cryptosporidiosis has risen approximately threefold in the United States (1). Cryptosporidium also has emerged as the leading etiology of nationally notified recreational water-associated outbreaks, particularly those associated with aquatic facilities (i.e., physical places that contain one or more aquatic venues [e.g., pools] and support infrastructure) (2). As of February 24, 2017, a total of 13 (54%) of 24 states reporting provisional data detected at least 32 aquatic facility-associated cryptosporidiosis outbreaks in 2016. In comparison, 20 such outbreaks were voluntarily reported to CDC via the National Outbreak Reporting System for 2011, 16 for 2012, 13 for 2013, and 16 for 2014. This report highlights cryptosporidiosis outbreaks associated with aquatic facilities in three states (Alabama, Arizona, and Ohio) in 2016. This report also illustrates the use of CryptoNet, the first U.S. molecularly based surveillance system for a parasitic disease, to further elucidate Cryptosporidium chains of transmission and cryptosporidiosis epidemiology. CryptoNet data can be used to optimize evidence-based prevention strategies. Not swimming when ill with diarrhea is key to preventing and controlling aquatic facility-associated cryptosporidiosis outbreaks (https://www.cdc.gov/healthywater/swimming/swimmers/steps-healthy-swimming.html).

Near Real-Time Surveillance of U.S. Norovirus Outbreaks by the Norovirus Sentinel Testing and Tracking Network - United States, August 2009-July 2015.

Norovirus is the leading cause of endemic and epidemic acute gastroenteritis in the United States (1). New variant strains of norovirus GII.4 emerge every 2-4 years (2-4) and are often associated with increased disease and health care visits (5-7). Since 2009, CDC has obtained epidemiologic data on norovirus outbreaks from state health departments through the National Outbreak Reporting System (NORS) (8) and laboratory data through CaliciNet (9). NORS is a web-based platform for reporting waterborne, foodborne, and enteric disease outbreaks of all etiologies, including norovirus, to CDC. CaliciNet, a nationwide electronic surveillance system of local and state public health and regulatory agency laboratories, collects genetic sequences of norovirus strains associated with gastroenteritis outbreaks. Because these two independent reporting systems contain complementary data, integration of NORS and CaliciNet records could provide valuable public health information about norovirus outbreaks. However, reporting lags and inconsistent identification codes in NORS and CaliciNet records have been an obstacle to developing an integrated surveillance system.

A State-by-State Assessment of Food Service Regulations for Prevention of Norovirus Outbreaks

Noroviruses are the leading cause of foodborne disease in the United States. Foodborne transmission of norovirus is often associated with contamination of food during preparation by an infected food worker. The U.S. Food and Drug Administration's Food Code provides model food safety regulations for preventing transmission of foodborne disease in restaurants; however, adoption of specific provisions is at the discretion of state and local governments. We analyzed the food service regulations of all 50 states and the District of Columbia (i.e., 51 states) to describe differences in adoption of norovirus-related Food Code provisions into state food service regulations. We then assessed potential correlations between adoption of these regulations and characteristics of foodborne norovirus outbreaks reported to the National Outbreak Reporting System from 2009 through 2014. Of the 51 states assessed, all (100%) required food workers to wash their hands, and 39 (76%) prohibited bare-hand contact with ready-to-eat food. Thirty states (59%) required exclusion of staff with vomiting and diarrhea until 24 h after cessation of symptoms. Provisions requiring a certified food protection manager (CFPM) and a response plan for contamination events (i.e., vomiting) were least commonly adopted; 26 states (51%) required a CFPM, and 8 (16%) required a response plan. Although not statistically significant, states that adopted the provisions prohibiting bare-hand contact (0.45 versus 0.74, P =0.07), requiring a CFPM (0.38 versus 0.75, P =0.09), and excluding ill staff for ≥24 h after symptom resolution (0.44 versus 0.73, P =0.24) each reported fewer foodborne norovirus outbreaks per million person-years than did those states without these provisions. Adoption and compliance with federal recommended food service regulations may decrease the incidence of foodborne norovirus outbreaks.

Mass Gatherings and Respiratory Disease Outbreaks in the United States - Should We Be Worried? Results from a Systematic Literature Review and Analysis of the National Outbreak Reporting System.

BackgroundBecause mass gatherings create environments conducive for infectious disease transmission, public health officials may recommend postponing or canceling large gatherings during a moderate or severe pandemic. Despite these recommendations, limited empirical information exists on the frequency and characteristics of mass gathering-related respiratory disease outbreaks occurring in the United States.MethodsWe conducted a systematic literature review to identify articles about mass gathering-related respiratory disease outbreaks occurring in the United States from 2005 to 2014. A standard form was used to abstract information from relevant articles identified from six medical, behavioral and social science literature databases. We also analyzed data from the National Outbreaks Reporting System (NORS), maintained by the Centers for Disease Control and Prevention since 2009, to estimate the frequency of mass gathering-related respiratory disease outbreaks reported to the system.ResultsWe identified 21 published articles describing 72 mass gathering-related respiratory disease outbreaks. Of these 72, 40 (56%) were associated with agriculture fairs and Influenza A H3N2v following probable swine exposure, and 25 (35%) with youth summer camps and pandemic Influenza A H1N1. Outbreaks of measles (n = 1) and mumps (n = 2) were linked to the international importation of disease. Between 2009 and 2013, 1,114 outbreaks were reported to NORS, including 96 respiratory disease outbreaks due to Legionella. None of these legionellosis outbreaks was linked to a mass gathering according to available data.ConclusionMass gathering-related respiratory disease outbreaks may be uncommon in the United States, but have been reported from fairs (zoonotic transmission) as well as at camps where participants have close social contact in communal housing. International importation can also be a contributing factor. NORS collects information on certain respiratory diseases and could serve as a platform to monitor mass gathering-related respiratory outbreaks in the future.

Outbreaks of Acute Gastroenteritis Transmitted by Person-to-Person Contact, Environmental Contamination, and Unknown Modes of Transmission — United States, 2009–2013

Acute gastroenteritis (AGE) is a major cause of illness in the United States, with an estimated 179 million episodes annually. AGE outbreaks propagated through direct person-to-person contact, contaminated environmental surfaces, and unknown modes of transmission were not systematically captured at the national level before 2009 and thus were not well characterized. 2009-2013. The National Outbreak Reporting System (NORS) is a voluntary national reporting system that supports reporting of all waterborne and foodborne disease outbreaks and all AGE outbreaks resulting from transmission by contact with contaminated environmental sources, infected persons or animals, or unknown modes. Local, state, and territorial public health agencies within the 50 U.S. states, the District of Columbia (DC), five U.S. territories, and three Freely Associated States report outbreaks to CDC via NORS using a standard online data entry system. A total of 10,756 AGE outbreaks occurred during 2009-2013, for which the primary mode of transmission occurred through person-to-person contact, environmental contamination, and unknown modes of transmission. NORS received reports from public health agencies in 50 U.S. states, DC, and Puerto Rico. These outbreaks resulted in 356,532 reported illnesses, 5,394 hospitalizations, and 459 deaths. The median outbreak reporting rate for all sites in a given year increased from 2.7 outbreaks per million population in 2009 to 11.8 outbreaks in 2013. The etiology was unknown in 31% (N = 3,326) of outbreaks. Of the 7,430 outbreaks with a suspected or confirmed etiology reported, norovirus was the most common, reported in 6,223 (84%) of these outbreaks. Other reported suspected or confirmed etiologies included Shigella (n = 332) and Salmonella (n = 320). Outbreaks were more frequent during the winter, with 5,716 (53%) outbreaks occurring during December-February, and 70% of the 7,001 outbreaks with a reported setting of exposure occurred in long-term-care facilities (n = 4,894). In contrast, 59% (n = 143) of shigellosis outbreaks, 36% (n = 30) of salmonellosis outbreaks, and 32% (n = 84) of other or multiple etiology outbreaks were identified in child care facilities. NORS is the first U.S. surveillance system that provides national data on AGE outbreaks spread through person-to-person contact, environmental contamination, and unknown modes of transmission. The increase in reporting rates during 2009-2013 indicates that reporting to NORS improved notably in the 5 years since its inception. Norovirus is the most commonly reported cause of these outbreaks and, on the basis of epidemiologic data, might account for a substantial proportion of outbreaks without a reported etiology. During 2009-2013, norovirus accounted for most deaths and health care visits in AGE outbreaks spread through person-to-person contact, environmental contamination, and unknown modes of transmission. Recommendations for prevention and control of AGE outbreaks transmitted through person-to-person contact, environmental contamination, and unknown modes of transmission depend primarily on appropriate hand hygiene, environmental disinfection, and isolation of ill persons. NORS surveillance data can help identify priority targets for the development of future control strategies, including hygiene interventions and vaccines, and help monitor the frequency and severity of AGE outbreaks in the United States. Ongoing study of these AGE outbreaks can provide a better understanding of certain pathogens and their modes of transmission. For example, certain reported outbreak etiologies (e.g., Salmonella) are considered primarily foodborne pathogens but can be transmitted through multiple routes. Similarly, further examination of outbreaks of unknown etiology could help identify barriers to making an etiologic determination, to analyze clinical and epidemiologic clues suggestive of a probable etiology, and to discover new and emerging etiologic agents. Outbreak reporting to NORS has improved substantially since its inception, and further outreach efforts and system improvements might facilitate additional increases in the number and completeness of reports to NORS.