Environmental Engineering Reference
In-Depth Information
Disinfection
The application of microbicidal chemicals to materials (surfaces
as well as water), which come into contact with or are ingested by humans
and animals, for the purpose of killing pathogenic microorganisms. Disin-
fection may not be totally effective against all pathogens.
Disinfestation
Any physical or chemical process serving to destroy or remove
undesired small animal forms, particularly arthropods or rodents, present
upon the person or the clothing, in the environment of an individual, or
on domestic animals. Disinfestation includes delousing for infestation with
Pediculus humanus
, the body louse. Synonyms include the terms
disinsec-
tion
and
disinsectization
when only insects are involved.
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Endemic
The constant presence of a disease or infectious agent within a
given geographic area; may also refer to the usual prevalence of a given
disease within such area.
Hyperendemic
expresses a persistent intense trans-
mission and
holoendemic
a high level of infection, beginning early in life
and affecting most of the population (e.g., malaria in some places).
Endotoxin
The toxin produced by a microorganism that is retained within
the cell but is liberated when the cell disintegrates (as in the intestine)
causing pathologic damage to surrounding tissue. Most known varieties of
these toxins withstand autoclaving.
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Enterotoxin
A toxin produced by certain microorganisms that is secreted
in the gastrointestinal tract. It is associated with the symptoms of food
poisoning and is heat stable. Examples of bacteria know to secrete this
type of toxin are:
Escherichia coli
O157: H7,
Clostridium perfringens
,
Vibrio cholerae
,
Staphylococcus aureus
,and
Yersinia enterocolitica
.
Epidemic/outbreak
The occurrence in a community or region of cases of an
illness in excess of what would be expected during the same time period.
The number of cases indicating the presence of an epidemic will vary
according to the infectious agent, size and type of population exposed,
previous experience or lack of exposure to the disease, and time and place
of occurrence; epidemicity is thus relative to usual frequency of the disease
in the same area, among the specified population, at the same season of
the year. A single case of a communicable disease long absent from a
population or the first invasion by a disease not previously recognized
in that area requires immediate reporting and epidemiologic investigation;
two cases of such a disease associated in time and place are sufficient
evidence of transmission to be considered an epidemic. The terms
outbreak
and
epidemic
can technically be used interchangeably; however, the public
perception of the latter is more dramatic.
Exotoxin
A toxin produced by a microorganism and secreted into the sur-
rounding medium, usually the cellular cytoplasm, blood, or other bodily
fluids. Exotoxins can operate on organs and tissues different from the site of
infection and can bring about pathological manifestations that are separate
from the initial infection, or within the infected cell itself. Genes encoding
exotoxins can be acquired by microorganisms that would otherwise cause
