Risk factors in patients with H1N1 influenza and other seasonal strains
| H1N1/09 | Other strains | p Value | |
| Smoking | |||
| Current | 109/363 (30%) | 18/61 (30%) | 0.1 |
| Past | 82 (23%) | 21/61 (34%) | |
| Non-smoker | 172 (47%) | 22/61 (36%) | |
| Asthma | 137/470 (29%) | 17/80 (21%) | 0.17 |
| Chronic obstructive pulmonary disease | 73/468 (16%) | 20/80 (25%) | 0.05 |
| Diabetes | 82/475 (17%) | 16/81 (20%) | 0.63 |
| Pregnancy* | 43/256* (9.5%) | 2/30* (2.5%) | 0.046 |
| Liver disease | 29/474 (4.9%) | 4/81 (6.2%) | 0.80 |
| Immunosuppressed | 80/473 (17%) | 12/80 (15%) | 0.74 |
| Current malignancy | 43/473 (9%) | 13/80 (16%) | 0.69 |
| Congestive cardiac failure | 31/472 (6.6%) | 8/80 (10%) | 0.24 |
| Ischaemic heart disease | 45/473 (9.7%) | 17/81 (21%) | 0.006 |
| Severe obesity | 68/276 (25%) | 7/46 (15%) | 0.19 |
| Chronic neurological disease | 52 (11%) | 8/81 (10%) | 0.84 |
| Chronic renal disease | 33/472 (7.0%) | 7/81 (8.6%) | 0.64 |
* Expressed as proportion of female patients.