The Epidemiology of Sapovirus in the Etiology, Risk Factors, and Interactions of Enteric Infection and Malnutrition and the Consequences for Child Health and Development Study: Evidence of Protection Following Natural Infection

Background. Sapovirus is one of the principal agents of acute viral enteritis in children. Because it has not been routinely included in diagnostic evaluations, the epidemiology and natural history remain poorly described. Methods. A birth cohort of 1715 children from 8 countries contributed surveillance samples (n = 35 620) and diarrheal specimens (n = 6868) from 0 to 24 months of age. Sapovirus was detected by quantitative polymerase chain reaction concurrently to other enteropathogens using multiarray cards. Logistic regression was used to identify risk factors, and longitudinal models were employed to estimate incidence rates and evaluate evidence of protective immunity. Results. Sapovirus was detected in 24.7% (n = 1665) of diarrheal stools and 12.8% (n = 4429) of monthly surveillance samples. More than 90% of children were infected and 60% experienced sapovirus diarrhea in the first 2 years of life. Breastfeeding and higher socioeconomic status were associated with reduced incidence of infection and illness. Specimens with sapovirus detected had an increased odds of coinfection with rotavirus (odds ratio [OR], 1.6 [95% confidence interval {CI}, 1.3–2.0]), astrovirus (OR, 1.5 [95% CI, 1.3–1.7]), adenovirus (OR, 1.3 [95% CI, 1.1–1.5]), and Shigella (OR, 1.4 [95% CI, 1.3–1.6]). Prior infection with sapovirus conferred a risk reduction of 22% for subsequent infection (hazard ratio [HR], 0.78 [95% CI, .74–.85]) and 24% for subsequent diarrhea (95% CI, 11.0%–35.0%; HR, 0.76). Conclusions. Sapovirus is a common cause of early childhood diarrhea. Further research on coinfections is warranted. Evidence of acquired immunity was observed even in the absence of genotype-specific analysis for this pathogen of known genetic diversity.