Table 1 Demographics of study population
| Â | Overall (n = 237) | Outbreak A (n = 149) | Outbreak B (n = 42) | Outbreak C (n = 46) |
|---|---|---|---|---|
Mean age (SE) (range) | 21.2 (1.7) (18.7-30.8) | 21.1 (2.1) (18.7-30.8) | 21.2 (0.8) (20.2-23.8) | 21.2 (0.5) (20.1-22.4) |
Median age (yr) | Â | Â | Â | Â |
Male | 237 (100%) | 149 (100%) | 42 (100%) | 46 (100%) |
Ethnicity | Â | Â | Â | Â |
   Chinese | 175 (73.8%) | 100 (67.1%) | 36 (85.7%) | 39 (84.8%) |
   Malay | 41 (17.3%) | 34 (22.8%) | 4 (9.5%) | 3 (6.5%) |
   Indian | 12 (5.1%) | 8 (5.4%) | 1 (2.4%) | 3 (6.5%) |
   Others | 9 (3.8%) | 7 (4.7%) | 1 (2.4%) | 1 (2.2%) |
Significant medical history | 25 (10.5%)* | 21 (14.1%) | 4 (9.5%) | 0 (0.0%) |