**2. Plants, man, and infectious diseases**

Man and plants as well as infectious agents have existed dating to time immemorable. The relationship between man, plants, and agents causing infectious diseases has not changed to this day. Plants provide us with shelter, nourishment, etc. Infectious diseases caused us infections. When we are infected by any of the infectious agents which you will read on later, we feel sick and experience abnormality in functions and sometimes structure.

Infectious agents have their route of entry or attachment to our body where they cause physiological changes. Some of these changes exhibit clinically on our skin, hands and nails, oropharynx, head and neck, eyes, neurons, heart and lungs, abdomen, musculoskeletal, and genitalia and rectum. Infections present with signs and symptoms some of which are unique to certain infectious agents. Signs include generalized erythema, splinter hemorrhages, finger clubbing, Janeway lesions, vasculitis, dental caries, candidiasis, tonsillar enlargement, lymphadenopathy, red eyes, neck stiffness, delirium, tachycardia, pericardial rub, ascites, joint swelling, discharge from the genitals, etc. [11]. When a man is infected with infectious diseases, the same plants that shelter man, and provide him with nutrients, etc. can again help man to battle infectious diseases.
