Norovirus is the leading cause of acute gastroenteritis (AGE) globally. Few longitudinal studies have assessed norovirus-associated AGE incidence across age groups in community settings in Latin America. During April 2015-April 2019, active surveillance for AGE among community members of all ages was conducted through household visits two to three times per week in San Jeronimo, Cusco, Peru. An asymptomatic control household was selected for every fifth AGE case. Stool specimens were collected from AGE cases, asymptomatic household members, and control household members, and they were tested for norovirus using real-time reverse transcriptase polymerase chain reaction. Data on illness characteristics were collected from AGE cases during a 15-day follow-up period. Annual means of 247 households and 1,555 participants were enrolled during each April-March surveillance year, accounting for 4,176 person-years (PY) of observation. Of 1,099 AGE events reported, 1,014 stool specimens were tested, and 186 (18%) were norovirus positive. Norovirus AGE incidence was 4.4/100 PY (95% CI: 3.9-5.1); incidence was highest among those younger than 2 years old (60.9/100 PY; 95% CI: 46.8-79.4). Among 672 stool specimens from asymptomatic controls, 56 (8%) tested positive for norovirus. Odds of norovirus detection were significantly higher among cases compared with controls (odds ratio: 2.2; 95% CI: 1.6-3.1). Age-stratified norovirus incidence in this periurban community aligns with previously published estimates and was highest among those younger than 2 years old. Establishing baseline norovirus incidence in specific communities is crucial to identify target populations and assess effectiveness of future interventions, such as vaccines.

While costs of norovirus acute gastroenteritis (AGE) to healthcare systems have been estimated, out-of-pocket and indirect costs incurred by households are not well documented in community settings, particularly in developing countries. We conducted active surveillance for AGE in two communities in Peru: Puerto Maldonado (October 2012-August 2015) and San Jeronimo (April 2015-April 2019). Norovirus AGE events with PCR-positive stool specimens were included. Data collected in follow-up interviews included event-related medical resource utilization, associated out-of-pocket costs, and indirect costs. There were 330 norovirus-associated AGE events among 3,438 participants from 685 households. Approximately 49% of norovirus events occurred among children <5 years of age and total cost to the household per episode was highest in this age group. Norovirus events cost a median of US $2.95 (IQR $1.04-7.85) in out-of-pocket costs and $12.58 (IQR $6.39-25.16) in indirect costs. Medication expenses accounted for 53% of out-of-pocket costs, and productivity losses accounted for 59% of the total financial burden on households. The frequency and associated costs of norovirus events to households in Peruvian communities support the need for prevention strategies including vaccines. Norovirus interventions targeting children <5 years of age and their households may have the greatest economic benefit.

BACKGROUND: While enteric viruses are highly transmissible, household factors associated with transmission are less well documented. We identified individual- and household-level factors associated with viral acute gastroenteritis (AGE) transmission in a large health care network in the United States. METHODS: Patients presenting with AGE were enrolled from April 2014 to September 2016. Patients and symptomatic household members were interviewed, and stool specimens were collected and tested for viral pathogens. Within a household, primary cases were those with the earliest symptom onset and a positive viral test result; secondary cases were household contacts (HHCs) with symptom onset 1-7 days from the primary case onset. Transmission households had at least 1 secondary case. RESULTS: Our analysis included 570 primary cases with 1479 HHCs. The overall secondary attack rate was 23%. HHCs were likely to become secondary cases (n = 338) if they were <5 years old (adjusted odds ratio [aOR], 1.8; 95% CI, 1.2-2.6). Secondary transmission was likely to occur if the primary case was aged <5 years (aOR, 2.2; 95% CI, 1.4-3.6) or 5 to 17 years (aOR, 3.3; 95% CI, 1.9-5.7), was norovirus positive (aOR, 2.7; 95% CI, 1.9-3.7), had a diapered contact (aOR: 2.2, 95% CI: 1.6-3.2), or reported symptoms for >4 days (aOR, 1.5; 95% CI, 1.1-2.1). Households with ≥3 members (aOR, 2.1; 95% CI, 1.1-4.5) were more likely to experience transmission. DISCUSSION: Risk of AGE transmission within households increased if the primary case was younger, was norovirus positive, had a longer symptom duration, or had a diapered contact. Targeted prevention messaging around appropriate cleaning, disinfection, and isolation of persons with AGE should be encouraged.

Knowledge of the epidemiology of sporadic acute gastroenteritis (AGE) in the United States is limited. During September 2016-September 2017, we surveyed Kaiser Permanente Northwest members in Oregon and Washington, USA, to collect data on the 30-day prevalence of dually defined AGE and diarrhea disease and related health-seeking behavior; from a subset of participants, we obtained a stool specimen. Using the iterative proportional fitting algorithm with raked weights, we generated AGE prevalence and annualized rate estimates. We detected norovirus, rotavirus, astrovirus, and sapovirus from submitted stool specimens through real-time quantitative reverse transcription PCR (qRT-PCR). We estimated a 30-day prevalence of 10.4% for AGE and 7.6% for diarrhea only; annual rates were 1.27 cases/person/year for AGE and 0.92 cases/person/year for diarrhea only. Of those with AGE, 19% sought medical care. Almost one quarter (22.4%) of stool specimens from those reporting AGE tested positive for ≥1 viral pathogen, compared with 8.2% from those without AGE.

OBJECTIVES: 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. METHODS: 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, 2 goodness-of-fit test, and Fisher exact test. RESULTS: 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; 110190 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. CONCLUSIONS: 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.

On May 11, 2022, the National Park Service (NPS) Office of Public Health (OPH) and Coconino County Health and Human Services (CCHHS) in Flagstaff, Arizona contacted CDC about a rising number of acute gastroenteritis cases among backcountry visitors to Grand Canyon National Park (Grand Canyon). The agencies reviewed illness report forms, assessed infection prevention and control (IPC) practices, and distributed a detailed survey to river rafters and hikers with backcountry permits (backpackers) who visited the Grand Canyon backcountry. During April 1-June 17, a total of 191 rafters and 31 backpackers reported symptoms consistent with acute gastroenteritis. Specimens from portable toilets used by nine river rafting trip groups were tested using real-time reverse transcription-polymerase chain reaction and test results were positive for norovirus. Norovirus-associated acute gastroenteritis is highly transmissible in settings with close person-to-person contact and decreased access to hand hygiene, such as backpacking or rafting. IPC assessments led to recommendations for regular disinfection of potable water spigots throughout the backcountry, promotion of proper handwashing with soap and water when possible, and separation of ill persons from those who are not ill. Prevention and control of acute gastroenteritis outbreaks in the backcountry requires rapid reporting of illnesses, implementing IPC guidelines for commercial outfitters and river rafting launch points, and minimizing interactions among rafting groups.

BACKGROUND: In the US, 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). METHODS: CDC collects epidemiologic and laboratory data on norovirus outbreaks from U.S. 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. RESULTS: 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 2009-2014 and median reporting of LTCF norovirus outbreaks stabilized at 4.1 outbreaks per 100 LTCFs (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 7,292 outbreaks with 862 (11.8%) positive for GI and 6,370 (87.3%) for GII. Among 4,425 GII outbreaks with typing data, 3,618 (81.8%) were GII.4. LTCF residents had higher attack rates than staff (median 29.0% versus 10.9%; p<0.001). For every 1,000 cases, there were 21.6 hospitalizations and 2.3 deaths. CONCLUSIONS: 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.

Acute gastroenteritis (AGE), characterized by diarrhea and vomiting, is an important cause of global mortality, accounting for 9% of all deaths in children under five years of age. Since the reduction of rotavirus in countries that have included rotavirus vaccines in their national immunization programs, other viruses such as norovirus and sapovirus have emerged as more common causes of AGE. Due to widespread use of real-time RT-PCR testing, sapovirus has been increasingly reported as the etiologic agent in both AGE outbreaks and sporadic AGE cases. We aimed to assess the role of sapovirus as a cause of endemic AGE worldwide by conducting a systematic review of published studies that used molecular diagnostics to assess the prevalence of sapovirus among individuals with AGE symptoms. Of 106 articles included, the pooled sapovirus prevalence was 3.4%, with highest prevalence among children <5 years of age (4.4%) and among individuals in community settings (7.1%). Compared to studies that used conventional RT-PCR, RT-qPCR assays had a higher pooled prevalence (5.6%). Among individuals without AGE symptoms, the pooled sapovirus prevalence was 2.7%. These results highlight the relative contribution of sapovirus to cases of AGE, especially in community settings and among children <5 years of age.