Definition of Infectious Diseases

Infectious disease is disease caused by a pathogen which enters the body and triggers the development of an infection. Infectious diseases have a range of causes, and they can be found all over the world. These diseases are considered contagious or communicable, meaning that they can be passed from person to person. It is also possible for such diseases to spread indirectly through unhygienic conditions, or from animals to people, in which case they are known as zoonotic diseases.

A variety of pathogens can be responsible for infectious disease, including viruses, bacteria, fungi, protozoans, and prions. Within these large categories of infectious organisms, there are numerous modes of transmission and a colorful assortment of symptoms, although surprisingly few organisms cause infectious disease, when one considers the diversity of viral, bacterial, fungal, and protozoan life. In order to treat an infectious disease, doctors must be able to knock out the source of the infection and repair the damage it has done to the body. Many infectious diseases make the body vulnerable to secondary infections, in which other organisms move in to take advantage of a weakened immune system, and this can be very problematic.

The study of infectious disease is known as epidemiology. Epidemiologists work to determine the source of an infectious disease so that they can develop new treatment approaches. They also identify emerging outbreaks, which may develop into epidemics or pandemics, and areas where a disease is endemic, meaning that it occurs regularly. Malaria, for example, is endemic to some regions of Africa and Southeast Asia. Read more »