Infectious Diseases: Descriptive Epidemiology, Transmission, Surveillance, Control

Abstract

We will be using the following definition of an infectious disease, which is short and focuses on the essential: An infectious disease is a disease caused by a microorganism. Sometimes, the term “communicable” is used as a synonym for “infectious” but we will avoid it because there is no general agreement about its meaning.By a microorganism we mean a living organism at the limit of visibility by the human eye or smaller. In essentially decreasing order of size, there are the following categories of microorganisms: Parasites and fungi. Bacteria including Rickettsia, Chlamydia, Spirochaeta and others. Viruses. Prions.