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INFECTIOUS DISEASES
AND TREATMENTS
3.1 Introduction
The presence of virulence factors, described in Chapter 2, 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 systemic
disease, 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.
In a text of this length, it is simply not possible to describe all diseases
caused by microorganisms. This chapter will concentrate on selected,
representative examples of infections of the major body systems and those
microorganisms that can produce a generalized infection. In addition, the
ways in which infectious diseases are prevented, investigated and treated
will be outlined.
OBJECTIVES