Lec2_Introduction_to_Infectious_Disease_Epidemiology

Lec2_Introduction_to_Infectious_Disease_Epidemiology -...

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Epidemiology of Infectious Diseases
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Epidemiology of Infectious Diseases Studies of the epidemiology of infectious diseases include evaluation of the factors leading to infection by an organism, factors affecting the transmission of an organism, and those associated with clinically recognizable disease among those who are infected
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Epidemiology of Infectious Diseases New infectious diseases can be classified according to their epidemiologic, clinical, or microbiologic features Knowledge of all of these features is important, however, knowledge of the epidemiologic features is of paramount importance for a public health professional who is concerned primarily with controlling or preventing the epidemic spread of an infection
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Epidemiology of Infectious Diseases Clinicians tend to classify infectious diseases according to their most common or most important clinical manifestation or by the organ systems that are most primarily affected Microbiologists tend to classify infectious diseases according to the characteristics of the causative organism Epidemiologists usually classify infectious diseases according to two important epidemiologic characteristics: means of transmission and reservoir of the organism
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Infectious Disease Epidemiology
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Portals of Exit and Entry Portals of Exit and Entry- the usual way that the agent leaves or escapes from the reservoir and the usual way that the agent enters the host Nose (secretions) Mouth (saliva, sputum) Broken skin (blood) Penis or Vagina (urine, semen or vaginal secretions) Anus (feces)
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Mode of transmission Mode of transmission- the mechanism by which the agent is physically transported from its reservoir or source to a new host There are three general modes: Direct Airborne Indirect
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Modes of Transmission Direct Airborne Indirect Vector-Borne Vehicle-Borne Mechanical Biological
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Mode of transmission Direct transmission: By direct or immediate transfer of the agent to an appropriate portal of entry by personal contact, e.g. touching, biting, kissing, sexual intercourse By the direct projection of droplets onto the new host (through sneezing, coughing), but this must occur over a very short distance ( 1 meter or less) to be considered direct Example of spread by direct transmission:
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Direct Transmission
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Mode of transmission Airborne transmission- Transfer of an infectious agent via air over longer distances (greater than 1 meter) Results when the agent can remain suspended in the air for longer periods of time and/or over larger areas Occurs when agents are suspended in either droplet nuclei (fluid) or attached to dust particles Examples of airborne transmission:
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Mode of transmission Indirect transmission: Requires less intimate contact with the source Two major types of indirect transmission are: Vehicle-borne Vector-borne
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Mode of transmission Vehicle borne- contaminated inanimate materials transfer the agent These include fomites:
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