| Onset type | Time of onset | No. | % |
| Early onset | 1st 24 hours | 36 | 24% |
| 2 - 3 days | 58 | 39% | |
| Late onset | >3 - 7 days | 20 | 13% |
| >7 days | 36 | 24% | |
| Total | 150 | 100% | |