Chapter 25, Problem 9MCQ

Summary Introduction

Introduction:

Microorganisms that have the ability to cause infectious diseases are called as pathogens. Such microorganisms include bacteria, fungi, virus, and protozoa. Illness in an individual is caused either by disturbing the normal metabolic activity of the host or by inducing the host’s immune system to produce a response. Infectious agents are transmitted by direct contact (person-to-person) or indirect contact (water-borne, food-borne, air-borne, soil-borne, fomite-borne, vector-borne, and zoonosis). Infectious diseases are responsible for the high frequency of human morbidity and mortality world-wide.