Infectious diseases spread through:
• Air: Causes air-borne diseases due to bacteria, virus e.g., common cold, influenza, measles, tuberculosis.
• Food and water: Is caused due to contaminated food and water that contains bacteria, virus, worm etc. Example, cholera, typhoid and hepatitis.
• Contact: Many diseases spread by contact of infected person with the healthy person. Examples, fungal infection, scabies etc.
AIDS and syphilis spread due to sexual contact.
• Body fluids: Body fluids like blood, semen, mother milk when infected can also cause disease. Example, AIDS.