Infectious Diseases and Treatments: Introduction

INFECTIOUS DISEASES AND TREATMENTS

INTRODUCTION

The presence of virulence factors, described, allows pathogenic microorganisms to infect specific body systems and cause a vast range of diseases. A small number of such organisms are also able to cause systemicdisease, that is one affecting the whole body. A pathogen must be transmitted from a source to the patient. Direct contact between hosts is the most obvious form of transmission but coughs and sneezes (aerosols), food, water and arthropod vectors are all used by various pathogens. The long-term survival of pathogenic microorganisms also depends on them maintaining their infectivity during transmission from host to host. The sources of pathogens can be abiotic, soil, water for example, or animals or other humans. Diseases that infect animals and humans are called zoonoses, while humans who harbor a pathogen but are symptomless are called carriers.