Spread of Disease

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Spread of Disease
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Epidemiology

• Epidemiology is the study of the
  patterns, causes, and effects of health and diseas
  e conditions in defined populations.
• Scientist who study the spread of disease are
  epidemiologists.

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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.

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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

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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.

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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.

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Transmission of Disease

• There are three main ways in which diseases are
  transmitted
• Contact
• Vehicle
• Vector

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Contact

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

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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

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Vector

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

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Disease Classification

• Endemic
• Common Source Outbreak
• Epidemic
• Pandemic

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Endemic Disease

• An endemic disease is one that is always present
  in a population.
• Ex. Influenza (A.K.A The Flu)

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Common Source Outbreak

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

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Epidemic

• An epidemic disease is a disease that many people
  acquire over a short period.
• Ex. Smallpox or Black Plague

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Pandemic

• A pandemic disease is a world-wide epidemic
  disease.
• Ex. Spanish Influenza or Polio

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Primary Source

• http//www.mansfield.ohio-state.edu/sabedon/biol2
  050.htm