Infectious diseases are divided into communicable and noncommunicable.
Transmissible infectious diseases can spread from the infected individual, through the skin or mucous membranes or indirectly, when an infected person contaminates the air through their breathing, an inanimate object or food.
In infectious diseases not transmissible microorganism is not contagious from one individual to another, but it requires special circumstances, whether environmental, accidental, and so on. For transmission. In these cases, infected people do not transmit the disease.
Treatment of Neurological Disorders with Intravenous Immunoglobulins by Gerard Said (Paperback – Jun 21, 2000)