Chapter 1 & 2 important definitions
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Plague- highly infectious, usually fatal epidemic disease./a serious, potentially life-threatening infectious disease
that is usually transmitted to humans by the bites of rodent fleas
Parasites – organism that grows, feeds, and is sheltered on or in a different organism and that does not contribute to
the survival of its host.
Parasitism – the intimate association of 2 different kinds of organisms wherein one benefits at the expense of the
Macro-parasites – composed of many cells, can be seen without the use of microscope; cycles through
transmission stages (eggs and larvae) which pass into the external environment, do not multiply in the host.
Virus – ultimate micro-parasite – smaller than bacteria; neither cells nor organisms; can only reproduce within their
host can be killed if their DNA or RNA is destroyed.
Incubation period -interval of time required for development of a disease
Latent period -seemingly inactive period between exposure to an infection and subsequent illness
Vector - an organism that transmits a pathogen from reservoir to host
Transmission – the movement of parasite from host to host whether direct or indirect.
Host – organism harboring another organism on or in itself
Agent – Biological, physical, chemical, psych osocial. Rate of growth, persistence. (eg.bacteria)
Environment- promote exposure of the disease (ex. Contaminated water)
Herd immunity – resistance of a group to a disease attack due to immunity.
Parasite virulence -capacity of a parasite to cause disease
Endemic – usual occurrence of a disease within a given geographical area
Epidemic – occurrence of a disease in excess of normal expectancy
Pandemic – worldwide epidemic
Pathogen- an infectious agent, or more commonly germ, is a biological agent that causes disease to its host.
Incidence - a measure of the risk of developing some new condition within a specified period of time.
Prevalence - the total number of cases of the disease in the population at a given time divided by the population. It
is used as an estimate of how common a condition is within a population over a certain period of time.
– the # of ppl each infected person infects at the beginning of an epidemic. It is the multiplier of the disease
which helps to predict how fast the disease will spread.
Dermal – disease transmission through the skin, e.g. fungus
Ingestion – disease transmission through the mouth, e.g. E.coli in water
Inhalation – disease transmission during respiration, e.g. particulate matter
Aspiration – disease transmission happens when something that’s supposed to go into stomach accidently goes into
the airway system.
Attack rate – ratio of the #people in whom a certain illness develops / total #people at risk
Measles – common skin rash, transmitted from respiration (around 94% must be immune)
Tuberculosis – infec tious disease that most commonly attacks the lungs. Many times no apparent symptoms.
Rabies – affec ts central nervous system, transmitted through saliva. Once sb gets it, it’s serious.
Type I Epidemic – pop
is large(300,000~500,000), pattern shows regular series of peaks, and disease never
completely disappears (endemic). Because # of susceptible ppl is large enough. Ro >1
Type II epidemic – peaks of infection is not continuous (not endemic), regular pattern of occurrence. Ro < 1
Type III epidemic – pattern of increase # of cases occur at irregular intervals, there are long periods when there are
no disease. Ro much smaller than 1. ( less than 10 ,000 of population.)
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