Patient-related risk factors for severe viral lung infections
| Chronic comorbidities Diabetes mellitus Hypertension Cardiovascular disease Cerebrovascular disease Chronic pulmonary disease Liver disease Immune impairments | There is a strong association between the number of underlying medical conditions and the severity of lung viral disease. |
| Age | A decline in immune function or immunosenescence increased patients’ susceptibility to infection and the risk of serious complications due to deterioration of function in both the acquired and innate immune system. Ageing and chronic comorbidities induce chronic endothelial dysfunction, which is related to vasoconstriction, inflammation and coagulation. The latter three physiologic processes may be related to the pathologic process occurring in severe lung infections such as influenza A virus, severe acute respiratory syndrome coronavirus (SARS-CoV), Middle Eastern respiratory syndrome coronavirus and SARS-CoV-2 infection. |
| Male sex | Influence of sex hormones on the immunologic response |
| Obesity | Diminished antibody response, immune deregulation due to adiposity and dysfunction of the immune adaptive immune system. Altered pulmonary mechanics and physiology. |
| Pregnancy | Immunologic alteration during pregnancy. Interplay between sex hormones that influence immune response. |