Disease: A state of non-well-being or ill health of the body or mind.
Epidemic: A simplified and crude definition is: the spread of a disease over a large number of individuals in
a given community in a particular, short, period of time.
Epidemiology: The study of the distribution of disease and injuries in human populations
Bacteria: Microscopic unicellular organisms capable of independent reproduction.
Endemic: The habitual presence or common recurrence of a disease in a population at a particular
Infectious disease: Able to be transmitted by air, water, foodstuffs, contact with objects, persons or
Pandemic: When the increased incidence of the disease is of global proportions. In other words, “a
pandemic is a worldwide epidemic” e.g 2009 h1n1
Scapegoat: an individual, or group of individuals, blamed for the origin or spread of a disease
Quarantine : The separation of individuals and/or goods, arriving from elsewhere and possibly carrying
disease, from a community. A state of quarantine could vary in duration depending on the disease and
the country of origin. Separate people who may have the disease
isolate (set apart people with the disease)
disease etiology: The causation, cause, reason (e.g. for the outbreak of a disease).
Cholera: An infectious disease of the small intestine, caused by a bacteria, resulting in severe vomiting,
diarrhoea, and possibly death.
Anti-contagionist: a.k.a. non-contagionist] the belief that a disease arose as a result of local causes (e.g.
miasma), not due to contact or importation from infected localities elsewhere.
cordon sanitaires: [a.k.a. sanitary cordon] a physical boundary, established by force, to separate a
community from outsiders.
Contagionists: Contagionist Theory of Disease: the belief that a disease could be transmitted through
contact with persons (i.e. person-to-person) or objects.
Miasmatists: Miasma: noxious vapours or smells, originating from organic matters in many cases, believed
by some to be the source of disease.
Bacillus: [plural = bacilli] rod-shaped, potentially pathogenic, bacterium.
Vibrio cholera : water-borne bacteria, typically shaped like a curved rod (e.g. the cholera bacterium).
Yellow fever: [a.k.a. black vomit fever] A tropical disease, caused by a virus and often transmitted via
mosquitoes, resulting in fever, jaundice, and possibly death.
Contagion: contagious disease
Epidemic curve: A graph of the distribution of cases (or deaths) according to the time of onset.
Mode of transmission: The means by which an infectious microbe is spread to and between human hosts.
Susceptible individuals : The quality of an individual who, by virtue of his/her biological and/or social
characteristics, is vulnerable to contract a disease once exposed to the micro-organism.
Case fatality rate: A measure of the severity of a disease. The proportion of people infected with a disease
who die from that disease within a specific time period [= number of deaths due to infectious disease X
number of cases of infectious disease X)*radix].
Herd immunity: The collective state of immunity, acquired by a population against a specific disease
Background mortality rate: The mortality rate prior to or excluding an outbreak of disease
Measles: Infectious air-borne disease, caused by a virus, resulting in red spots on the skin.
Reservoir: The niche in which a micro-organism lives and reproduces.
Carrier states: (Asymptomatic carriers): An individual who carriers the disease but does not display any
symptoms. Carriers may be inapparent, incubatory, or convalescent. Inapparent carriers are individuals
who are free of a disease but can transmit the disease agent. Incubatory carriers are individuals who are
in the early stages of infection. They do not yet show symptoms themselves, but are capable of
transmitting the disease agent. Convalescent carriers are individuals who have recovered from a disease
but are still capable of transmitting it to others.
Life-long immunity: A measure of a host's resistance to a particular disease or disease complex. May be
genetic, acquired, maternally-derived, or produced through active immunization.
Zoonotic diseases: Disease of animal origin. They may be passed to humans via animal carriers.
Immigration: Movement of people into a community
Emigration: Movement of people out of a community.
Virgin soil population: A population with no prior exposure to a particular disease. Members of such a
community experience heightened mortality during an epidemic since everyone is susceptible.
Risk : The probability of becoming a case (diseased) during a defined time interval, from among those
who, at the beginning of the interval, were not a case and who at the end of the interval did not die from
Morbidity rate: Proportion of people with a disease in a population within a specific time period (=number
of individuals who become ill from an infectious disease ÷
number of individuals available to be infected)
Radix: A multiplier used in the computation of a health measure to raise the value to a whole number
(typically 1000, 10 000 or 100 000).