i.Age

Advanced age has been shown to be a risk factor for severe illness, complications, and death. Children usually present with mild symptoms.

ii.Underlying medical condition and smoking

Patients without underlying medical conditions have a better prognosis compared with those with comorbidities such as heart disease, hypertension, prior stroke, diabetes, chronic lung disease, and chronic kidney disease who have been associated with increased illness severity and adverse outcomes. Smoking has also been linked to increased risk for severe disease.