SPREAD OF DISEASE

Epidemiology

Epidemiology: is the study of the patterns, causes, and effects of health and disease conditions in defined populations.

Scientist who study the spread of disease are epidemiologists.

Sources of Infectious Diseases

• The source of a disease is known as a reservoir.

• A reservoir can be anything: inanimate object, person, animal, plant, etc.

• The reservoir of a disease is not necessarily affected by the disease

Ex. 2009 a women boarded a plane at JFK airport in New York with Tuberculosis. This women did not have any signs of TB. She found out she had it when the disease spread to 12 other passengers, killing two of them.

Carrier

The most important type of reservoir in human disease is known as a carrier.

A carrier is a person who carries (is infected by) a communicable disease

A carrier of a disease may not have symptoms

Animal Reservoir

A zoonosis is a communicable disease which is transmitted from a non-human animal to a human.

Here the non-human animal is the reservoir.About 150 zoonotic human disease are known.Examples: anthrax, bubonic plague, cat-scratch fever, influenza, Lyme disease, malaria, pneumonic plague, psittacosis, rabies, ringworm, Rocky Mountain spotted fever, tapeworm, toxoplasmosis, typhus fever, western equine encephalitis, yellow fever.

Endogenous Infection - FYI

An endogenous infection is one which is caused by an opportunistic pathogen from an individual's own normal microbiota.

Typically this is a consequence either of the individual being in a weakened state, or in the opportunist being deposited in a location other than that in which it typically benignly resides.

Transmission of Disease

There are three main ways in which diseases are transmitted

• Contact• Vehicle• Vector

Contact

• Diseases can be spread by direct contact (person to person), indirect contact (doorknob), or by droplets (released into the air when sneezing)

Vehicle

• A vehicle is something that is taken into the body as part of living (food, water, air)

• When contaminated, these things can cause disease

Vector

• Vectors are organisms that transmit infections from one host to another

• They are usually insects

Disease Classification

• Endemic• Common Source Outbreak• Epidemic• Pandemic

Endemic Disease

• An endemic disease is one that is always present in a population.

Ex. Influenza (A.K.A: The Flu)

Common Source Outbreak

• Some diseases arise from a single definable source, such as a common water supply.

Epidemic

• An epidemic disease is a disease that many people acquire over a short period.

Ex. Smallpox or Black Plague

Pandemic

• A pandemic disease is a world-wide epidemic disease.

Ex. Spanish Influenza or Polio

Primary Source

http://www.mansfield.ohio-state.edu/~sabedon/biol2050.htm