Results
Among all the articles screened for selection in the meta-analysis, 43 were analyzed (Supplementary appendix 1). No study reported the incubation period outside Asia. In total, 12 (27.9%) cohorts and 31 (72.1%) case reports and series were gathered, with a median age of 40.1 years, and a sex ratio greater than 1. The median sample size was estimated at 56 [IQR 16 ; 163] individuals.
Figure 1 shows that the mean incubation period is equal to 6.24 days 95% CI [5.80;6.69] ranging from 2.33 to 17.60 days. A magnitude of 15.27 days was described among the studies analyzed. In addition, studies are substantially heterogeneous (I2 = 95%) between each other.
In meta-regression or by subgroup analysis, this large amount of heterogeneity across studies could be explained by difference between studies in gender distribution or study design. Shorter incubation periods were reported in cohorts compared to case series (p<0.01) and among studies with high proportions of males (p<0.05). However, no significant variation was identified by age.