Table 1.

Demographics of all serum sample donors (n = 1013)

Group	Beijing, n (%)	Jiangsu, n (%)	Freetown, n (%)	Total, n (%)
Age (years)
≤30	48 (18.8%)	40 (15.4%)	244 (49.0%)	332 (32.8%)
31–40	69 (27.1%)	74 (28.5%)	146 (29.3%)	289 (28.5%)
41–50	63 (24.7%)	86 (33.1%)	108 (21.7%)	257 (25.4%)
>50	75 (29.4%)	60 (23.1%)	0 (0)	135 (13.3%)
Gender
Male	120 (47.1%)	123 (47.3%)	268 (53.8%)	511 (50.4%)
Female	135 (52.9%)	137 (52.7%)	230 (46.2%)	502 (49.6%)
Total	255 (100%)	260 (100%)	498 (100%)	1013 (100%)