| Genotype | Clinical isolates N (%) | Environmental isolates N (%) | ||||
| Serotype A | Serotype D | Total | Serotype A | Serotype D | Total | |
| VNI | 47 | 1 | 48 (28%) | 22 | 0 | 22 (69%)c |
| VNII | 2 | 0 | 2 (1%) | 0 | 0 | 0 |
| VNIII | 20 | 1 | 21 (12%) | 0 | 0 | 0 |
| VNIV | 8 | 91 | 99 (58%)a | 0 | 10 | 10 (31%) |
| Total | 77 (45%) | 93 (55%) | 170 | 22 (69%)b | 10 (31%) | 32 |