| Category | Risk Factor |
| Non-modifiable | Extreme age group (Age > 65 years old and neonates) |
| Cardiovascular | Chronic smoking Hypertension Poorly controlled diabetes mellitus Previous history of stroke Hyperlipidaemia Congestive heart failure |
| Immunocompromised State | Long term steroid usage Rheumatological disease Liver cirrhosis End stage renal failure Acquired Immunodeficiency Syndrome Active Malignancy Recent Chemotherapy |