infectious disease

An infectious disease is a disease caused by any microorganism, but particularly viral and bacterial diseases and parasitic diseases, in which the causative agent may be transferred from one person to another (directly or indirectly). Knowledge of the stages at which a particular disease is liable to infect others and of its route (via skin scales, cough particles, clothing, urine, feces, saliva, or by insects, particularly mosquitoes and ticks) helps physicians to limit the spread of disease in epidemics.