Forest plot of viral infection data. Plot shows meta-analysis result of all assessed studies reporting number of infections. Subgroup analysis according to the sample origin is also shown. Blue squares indicate the relative weight of each study in the meta-analysis and horizontal lines represent the 95% CI for the effect size. Larger squares show studies with higher relative weights. Weights are from random-effects analysis and are based on the size of the study and the number of events. Red diamonds represent the total effect size.