lecture 1

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2 Nov 2010
Disease transmission
: organism that grows, feeds, and is sheltered on or in a different
organism (host) and does not contribute to the survival of its host
: ultimate micro-parasite - smaller than bacteria; neither cells nor organisms;
can only reproduce within their host
: composed of many cells; does not multiply in a host, instead it
lives certain cycles/stages through transmission stages - eggs and larvae which
passes into the external environment
: movement from a parasite from host or host (direct or indirect)
Incubation period
: interval of time required for a development of a disease
Latent period
: seemingly inactive period between exposure to an infection and
subsequent illness
Parasite virulence
: capacity of a parasite to cause disease (ability)
Zoonotic infections
: animal infections that can be transmitted to humans
Main factors that influence the occurrence of a disease -
- Three main factors:
[factors: immunity, genetics, nutrition]
[biological, physical, chemical, psychosocial; rate of
growth; persistence]
[promotes exposure]
A person develops severe cramps after drinking from a well located on a cattle farm -
host: person, environment: contaminated water, agent: bacterium
Modes of disease transmission
- Direct - through direct contact (person to person)
- Indirect - through a common route (air, water, mosquito)
Portal of entry:
- Dermal - through the skin (fungi)
- Ingestion - through the mouth (e coli in water)
- Inhalation - during respiration (particulate matter)
Types of diseases
Iceberg concept - spectrum of disease severity
Host response
Death of organism
Classical and severe disease clinical
Moderate severity, mild illness disease
Infection without clinical illness (asymptomatic infection) subclinical
Exposure without infection disease
: infectious disease that most commonly attacks the lungs
: common skin rash, transmitted from respiration
: affects central nervous system, transmitted through saliva
Types of disease outbreaks
: usual occurrence of a given disease with a given geographical area
(certain area)
: occurrence of a disease in excess of normal expectancy in a defined
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