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The same as in Fig. 3, but for prevalence of norovirus asymptomatic infection under outbreaks circumstance (τ2 = 1.42, P < 0.01 test for heterogeneity) from 15 studies. The length of confidence interval corresponded to the sample size of the study and therefore the precision of the estimate.
*. Studies with prevalence were calculated in N outbreaks (N > 1).
