Figure 3. Spatial Spread of ZEBOV.

(A) Relationship between date and longitude of outbreaks in Gabon-Congo border area. Blue squares, human outbreaks [2] and 2003 outbreak at Mbandza village; red circles, animal carcasses testing positive for Ebola [18]; gray diamonds, ape die-off at Ibounji\Lokoue clearing. Regression line is for pooled data. Analyzed separately, human outbreaks and Ebola+ animal carcasses both show significant correlations between longitude and date (human outbreaks n = 12, R² = 0.48, p = 0.01; animal carcasses n = 13, R² = 0.91, p < 0.001).

(B) Added are 1996 human outbreak at Booué and Ebola+ chimpanzee carcass from nearby Lope [1]. The lack of reported human outbreaks between 1996 and 2001 may simply reflect the extremely low village density between Booué and Mendemba (Figure 1).

(C) Time after Yambuku versus straight line distance from Yambuku to all subsequent human outbreaks, including [2,14] and Mbandza village (R² = 0.42, n = 17, p = 0.005).

(D) Same as (C) but with distance from Yambuku to the recent Gabon-Congo border outbreaks measured as passing through Booué (R² = 0.97,n =17, p < 0.001). All figures include outbreak sites cited [2,14] for which no ZEBOV-GP sequences were publicly available.