Infectious diseases are caused by living in or on humans, animals, or plants.

Microorganisms such as bacteria, viruses, or fungi.

Explanation:

They can be passed from person to person through body secretions, insects or other means. Examples are SARS, influenza, the common cold, tuberculosis (TB), Hepatitis A and B.

starvation is bad because your body needs nutrition and to deprive it of nutrition can cause problems with both health and fitness.

explanation:

it can make weight loss slow down over time, but it won't cause someone to gain weight depsite restricting calories. starvation causes weakness in the senses like thirst.