Table 1.
Incidence and Percentage of Children Infected by Norovirus and With Norovirus-associated Diarrhea as Reported by Birth Cohort Studies
| Birth Cohorta [Reference] | Incidence of Norovirus Infection (per 100 Child-Years) | Percentage of Children Infected by Norovirus | Incidence of Norovirus Diarrhea (per 100 Child-Years)b | Percentage of Children With Norovirus-associated Diarrhea |
|---|---|---|---|---|
| MAL-ED [29] | Incidence overall in MAL-ED: 157. Nepal: 40; Tanzania: 105; Brazil: 120; Pakistan: 148; South Africa: 189 India: 194; Bangladesh: 221; Peru: 235 |
86% had at least 1 infection by age 1; 89% had at least 1 infection by age 2; 54% had at least 1 GI infection by age 2; 84% had at least 1 GII infection by age 2 | Incidence overall in MAL-ED not reported. Nepal: 36; Peru: 216; other countries not reported | 16% had at least 1 diarrheal episode with GI present by age 2; 36% had at least 1 diarrheal episode with GII present by age 2 |
| Peru [24] | 146 | 80% had at least 1 infection by age 1; 38% had at least 2 infections by age 1 | 66 | 38% had at least 1 diarrheal episode with norovirus present by age 1; 71% had at least 1 diarrheal episode with norovirus present by age 2 |
| Ecuador [28] | 51 (95% CI, 45–58) | 66% had at least 1 infection by age 3; 40% had 2 infections by age 3; 16% had >2 infections by age 3 | 17 (95% CI, 14–21) | 30% had at least 1 diarrheal episode with norovirus present by age 3; 10% had >1 diarrheal episode with norovirus present by age 3 |
| India [20, 21] | Not reported | 4% had at least 1 asymptomatic infection by age 3 | 14 | 40% had at least 1 diarrheal episode with norovirus present by age 3 |
| Brazil [17] | Not reported | 60% had at least 1 asymptomatic infection by age 3 | Not reported | 55% had at least 1 diarrheal episode with norovirus present by age 3 |
| Chile [23] | 112 | 57% had at least 1 asymptomatic infection by 18 mo | 13 | Percentages not reported |
Abbreviations: CI, confidence interval; GI, genogroup I; GII, genogroup II; MAL-ED, Etiology, Risk Factors and Interactions of Enteric Infections and Malnutrition and the Consequences for Child Health and Development.
aBirth cohort studies in Mexico [18, 19], Bangladesh [26, 36], and Vietnam [35] did not report incidence or the percentage of children infected with norovirus or with norovirus-associated diarrhea. Birth cohort studies in India, Brazil, and Chile reported the percentage of children asymptomatically infected by norovirus rather than the percentage of total norovirus infections.
bPercentages were reported directly from the manuscript text. The following numbers of children were followed for the analysis conducted in each study: 199 (MAL-ED), 291 (Peru), 194 (Ecuador), 173 (asymptomatic) [21] or 373 (diarrheal) [20] (India), 20 (Brazil), 198 (Chile). Incidence estimates were reported directly from text (Ecuador) or calculated from the reported number of infections divided by the child-months of follow-up (MAL-ED, Peru, Chile). All incidence estimates were converted to units of 100 child-years for ease of comparison.