Background: Acute gastroenteritis (AGE) is a leading infectious cause of morbidity worldwide, particularly among children in developing countries. With the decline of rotavirus disease rates following introduction of rotavirus vaccines, the relative importance of norovirus will likely increase. The objectives of this study were to determine the incidence and clinical profile of norovirus disease in Guatemala. Methods: We analyzed data from a population-based surveillance study conducted in Guatemala from 2008-2013. Demographics information, clinical data, and stool samples were collected from patients presenting with AGE (>/=3 liquid stools within 24-hours that initiated 7 days before presentation). Estimated incidence of hospitalized, outpatient, and total community norovirus disease was calculated using surveillance data and household surveys of healthcare utilization. Results: We included 999 AGE hospitalizations and 3,189 AGE outpatient visits at facilities, of which 164 (16%) and 370 (12%), respectively, were positive for norovirus. Severity of norovirus was milder than rotavirus. Community incidence of norovirus ranged between 2068-4954 per 100,000 person-years (py) in children <5 years of age. Children <5 years also had higher incidence of norovirus-associated hospitalization (51-105 per 100,000 py) compared with patients aged >/=5 years (0-1.6 per 100,000 py and 49-80 per 100,000 py, respectively). Conclusion: This study highlights the burden of norovirus disease in Guatemala, especially among young children. These data can help prioritize development of control strategies, including the potential use of vaccines, and provide a baseline to evaluate the impact of such interventions.

BACKGROUND: In the Unites States, long-term care facilities (LTCFs) are the most common setting for norovirus outbreaks. These outbreaks provide a unique opportunity to better characterize the viral and host characteristics of norovirus disease. METHODS: We enrolled 43 LTCFs prospectively to study the epidemiology, virology, and genetic host factors of naturally occurring norovirus outbreaks. Acute and convalescent stool, serum, and saliva samples from cases, exposed and nonexposed controls were collected. Norovirus infection was confirmed using quantitative polymerase chain reaction testing of stool samples or 4-fold increase in serum antibody titers. The presence of histo-blood group antigens (secretor, ABO, and Lewis type) was determined in saliva. RESULTS: Sixty-two cases, 34 exposed controls, and 18 nonexposed controls from 10 norovirus outbreaks were enrolled. Forty-six percent of acute, 27% of convalescent case, and 11% of control stool samples tested norovirus positive. Outbreak genotypes were GII.4 (Den Haag, n = 3; New Orleans, n = 4; and Sydney, n = 2) and GI.1 (n = 1). Viral load in GII.4 Sydney outbreaks was significantly higher than in outbreaks caused by other genotypes; cases and controls shed similar amounts of virus. Forty-seven percent of cases shed virus for ≥21 days. Symptomatic infections with GII.4 Den Haag and GII.4 New Orleans were detected among nonsecretor individuals. CONCLUSIONS: Almost half of all symptomatic individuals shed virus for at least 21 days. Viral load was highest in GII.4 viruses that most recently emerged; these viruses also infect the nonsecretor population. These findings will help to guide development of targeted prevention and control measures in the elderly.