| years | Number of samples checked | Total positive | ||||
| No. of positive | Different species | |||||
|
|
|
| Pf | Pv | Pf + Pv | |
| 1992 | 99,672 | 214 | 80 | 188 | 25 | |
| 1993 | 153,000 | 400 | 157 | 168 | 74 | |
| 1994 | 97,862 | 178 | 82 | 79 | 30 | |
| 1995 | 96,321 | 117 | 41 | 63 | 13 | |
| 1996 | 106,456 | 203 | 99 | 81 | 22 | |
|
| 553,311 | 1112 0.2% | 459 41.3% | 579 52.1% | 168 15.1% | |