Tropical Medicine
1. Carrier
A person or animal that harbors a specific infectious agent without
discernible clinical disease and serves as a potential source of infection.
The carrier state may exist in an individual with an infection that is
unapparent throughout its course (commonly known as healthy or a
symptomatic carrier), or during the incubation period, convalescence and
post convalescence of an individual with a clinically recognizable disease
(commonly known as an incubatory or convalescent carrier). Under either
circumstance the carrier state may be of short or long duration (temporary
or transient carrier, or chronic carrier).
2. Case-fatality rate
Usually expressed a the percentage of persons diagnosed as having a
specified disease who die as a result of that illness within a given
period. This term is most frequently applied to a specific outbreak of
acute disease in which all patients have been followed for an adequate
period of time to include all attributable deaths. The case-fatality rate
must be clearly differentiated from the mortality rate (q.v.). (Synonyms:
fatality rate, fatality percentage, case-fatality ratio).
3. Chemoprophylaxis
the administration of a chemical, including antibiotics, to prevent
the development of an infection or the progression of an infection to
active manifest disease, or to eliminate the carriage of a specific
infectious agent to prevent transmission and disease in others.
Chemotherapy, on the other hand, refers to use of a chemical to treat a
clinically manifest disease or to limit its further progress.
4. Cleaning
The removal by scrubbing and washing, as with hot water, soap or
suitable detergent or by vacuum cleaning, of infectious agents and of
organic matter from surfaces on which and in which infectious agents may
find favorable conditions for surviving or multiplying.
5. Communicable disease
An illness due to a specific infectious agent or its toxic products
that arises through transmission of that agent or its products from an
infected person, animal or inanimate reservoir to a susceptible host;
either directly or indirectly through an intermediate plant or animal host,
vector or the inanimate environment. (Synonym: infectious disease).
6. Communicable
period
The time during which an infectious agent may be transferred directly
or indirectly from an infected person to another person, from an infected
animal to humans, or from an infected person to animals, including
arthropods.
In diseases such as diphtheria and streptococcal infection, in which
mucous membranes are involved from the initial entry of the infectious
agent, the period of communicability is from the date of first exposure to
a source of infection until the infecting microorganism is no longer
disseminated from the involved mucous membranes, i.e., from the period
before the prodromata until termination of a carrier state, if the latter
develops. Some diseases are more communicable during the incubation period
than during the actual illness (e.g., hepatitis A, measles).
In diseases such as tuberculosis, leprosy, syphilis, gonorrhea and some of
the salmonelloses, the communicable state may exist over a long and
sometimes intermittent period when active chronic lesions permit the
discharge of infectious agents from the surface of the skin or through any
of the body orifices.
In diseases transmitted by arthropods, such as malaria and yellow fever,
the periods of communicability (or more properly infectivity) are those
during which the infectious agent occurs in the blood or other tissues of
the infected person in sufficient numbers to permit infection of the
vector. A period of communicability (transmissibility) is also to be noted
for the arthropod vector, namely, when the agent is present in the tissues
of the arthropod in such form and locus (infective state) as to be
transmissible.
7. Contact
A person or animal that has been in such association with an infected
person or animal or a contaminated environment as to have an opportunity
to acquire the infection.
8. Contamination
The presence of an
infectious agent on a body surface, in clothes, bedding, toys, surgical
instruments or dressings, or other inanimate articles or substances
including water and food. Pollution is distinct from contamination and
implies the presence of offensive, but not necessarily infectious matter
in the environment. Contamination of a body surface does not imply a
carrier state.
9. Disinfection
Killing of infectious agents outside the body by direct exposure to
chemical or physical agents. High-level disinfection may kill all
microorganisms with the exception of high numbers of bacterial spores; it
requires extended exposure to ensure killing of most bacterial spores. It
is achieved, after thorough detergent cleaning, by exposure to specific
concentrations of certain disinfectants (e.g., 2% glutaraldehyde, 6%
stabilized hydrogen peroxide and up to 1% peracetic acid) for at least 20
minutes. Intermediate-level disinfection does not kill spores; it can be
achieved by pasteurization (75%C [167°F] for 30 minutes) or by
appropriate treatment with EPA approved disinfectants.
Concurrent disinfection is the application of disinfective measures a soon
as possible after the discharge of infectious material from the body of an
infected person, or after the soiling of articles with such infectious
discharges; all personal contact with such discharges or articles should
be minimized prior to such disinfection.
Terminal disinfection is the application of disinfective measures after
the patient has been removed by death or to a hospital, or has ceased to
be a source of infection, or after hospital isolation or other practices
have been discontinued. Terminal disinfection is rarely practiced;
terminal cleaning generally suffices (see Cleaning), along with airing and
sunning of rooms, furniture and bedding. Disinfection is necessary only
for diseases spread by indirect contact; steam sterilization or
incineration of bedding and other items is recommended after a disease
such as Lassa fever or other highly infectious diseases.
Sterilization involves destruction of all forms of life by heat,
irradiation, gas (ethylene oxide or formaldehyde) or chemical treatment.
10. Disinfestation
Any physical or chemical process serving to destroy or remove
undesired small animal forms, particularly arthropods or rodents, present
upon the person, the clothing, or in the environment of an individual, or
on domestic animals. (See Insecticide and Rodenticide). Disinfestation
includes delousing for infestation with Pediculus humanus, the human body
louse. Synonyms include the terms disinsection and disinsectization when
only insects are involved.
11. Endemic
the constant presence of a disease or infectious agent within a given
geographic area; it may also refer to the usual prevalence of a given
disease within such area. hyperendemic expresses a constant presence at a
high level of incidence, and holoendemic a high level of prevalence with
infections beginning early in life and affecting most of the population,
e.g., malaria in some places. (See Zoonosis).
12. Epidemic
The occurrence in a community or region of cases of an illness (or an
outbreak) with a frequency clearly in excess of normal expectancy. The
number of cases indicating 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, an 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. (See Report of a
Disease and Zoonosis).
13. Food irradiation
A technology that provides a specific dose of ionizing radiation from
a source such as a radioisotope (e.g., Cobalt 60), or from machines that
produce accelerated electron beams or x-rays. Doses for irradiation of
food and materiel are: low, 1 or less kiloGrays (kGy), used for
disinfestation of insects from fruit, spices and grain; and parasite
disinfection from fish and meat; medium, 1-10 kGy (commonly 1-4 kGy), used
for pasteurization and the destruction of bacteria and fungi; and high,
10-50 kGy, used for sterilization of food as well as medical supplies (including
IV fluids, implants, syringes, needles, thread, clips and gowns).
14. Fumigation
Any process by which the killing of animal forms, especially
arthropods and rodents, is accomplished by the use of gaseous agents (See
Insecticide and Rodenticide).
15. Health education
Health education is the process by which individuals and groups of
people learn to behave in a manner conducive to the promotion, maintenance
or restoration of health. Education for health begins with people as they
are, with whatever interests they may have in improving their living
conditions. Its aim is to develop in them a sense of responsibility for
health conditions, as individuals and as members of families and
communities. In communicable disease control, health education commonly
includes an appraisal of what is known by a population about a disease, an
assessment of habits and attitudes of the people as they relate to spread
and frequency of the disease, and the presentation of specific means to
remedy observed deficiencies. (Synonyms: patient education, education for
health, education of the public, public health education).
16. Herd immunity
The immunity of a group o community. The resistance of a group to
invasion and spread of an infectious agent, based on the resistance to
infection of a high proportion of individual members of the group.
17. Host
A person or other living animal, including birds and arthropods, that
affords subsistence or lodgment to an infectious agent under natural (as
opposed to experimental) conditions. Some protozoa and helminths pass
successive stages in alternate hosts of different species. Hosts in which
the parasite attains maturity or passes its sexual stage are primary or
definitive hosts; those in which the parasite is in a larval or asexual
state are secondary or intermediate hosts. A transport host is a carrier
in which the organism remains alive but does not undergo development.
18. Immune individual
A person or animal that has specific protective antibodies and/or
cellular immunity as a result of previous infection or immunization, or is
so conditioned by such previous specific experience as to respond in such
a way that prevents the development of infection and/or clinical illness
following reexposure to the specific infectious agent. Immunity is
relative: a level of protection that could be adequate under ordinary
conditions may be overwhelmed by an excessive dose of the infectious agent
or by exposure through an unusual portal of entry; protection may also be
impaired by immunosuppressive drug therapy, concurrent disease or the
aging process. (See Resistance).
19. Immunity
That resistance usually associated with the presence of antibodies or
cells having a specific action on the microorganism concerned with a
particular infectious disease or on its toxin. Effective immunity includes
both cellular immunity, which is conferred by T-lymphocyte sensitization,
and/or humoral immunity, which is based on B-lymphocyte response. Passive
immunity is attained either naturally by transplacental transfer from the
mother, or artificially by inoculation of specific protective antibodies (from
immunized animals, or convalescent hyperimmune serum or immune serum
globulin [human]; it is of short duration (days to months). Active humoral
immunity, which usually lasts for years, is attained either naturally by
infection with or without clinical manifestations, or artificially by
inoculation of the agent itself in killed, modified or variant from, or of
fractions or products of the agent.
20. Inapparent infection
the presence of infection in a host without recognizable clinical
signs or symptoms. Inapparent infections are identifiable only by
laboratory means such as a blood test or by the development of positive
reactivity to specific skin tests. (Synonyms: asymptomatic, subclinical,
occult infection).
21. Incidence rate
The number of new cases of a specified disease diagnosed or reported
during a defined period of time, divided by the number of persons in a
stated population in which the cases occurred. This is usually expressed
as cases per 1’000 or 100’000 per annum. This rate may be expressed as
age- or gender-specific or as specific for any other population
characteristic or subdivision. (See Morbidity rate and prevalence rate).
Attack rate, or case rate, is a proportion measuring cumulative incidence
often used for particular groups, observed for limited periods and under
special circumstances, as in an epidemic; it is usually expressed as
percent (cases per 100 in the group). The secondary attack rate is the
number of cases among familial or institutional contacts occurring within
the accepted incubation period following exposure to a primary case, in
relation to the total of exposed contacts; the denominator may be
restricted to susceptible contacts when determinable. Infection rate is a
proportion that expresses the incidence of all identified infections,
manifest and in apparent.
22. Incubation period
The time interval between initial contact with an infectious agent and
the first appearance of symptoms associated with the infection. In a
vector, it is the time between entrance of an organism into the vector and
the time when that vector can transmit the infection (extrinsic incubation
period). The period in people between the time of exposure to a parasite
and the time when the parasite can be detected in blood or stool is called
the prepatent period.
23. Infected individual
A person or animal that harbors an infectious agent and who has either
manifest disease (see Patient or sick person) or in apparent infection (see
Carrier). An infectious person or animal is one from whom the infectious
agent can be naturally acquired.
24. Infection
The entry and development (of many parasites) or multiplication of an
infectious agent in the body of persons or animals. Infections is not
synonymous with infectious disease; the result may be inapparent (see
Inapparent infection) or manifest (see Infectious disease). The presence
of living infectious agents on exterior surfaces of the body, or on
articles of apparel or soiled articles, is not infection, but represents
contamination of such surfaces and articles. (See Infestation and
Contamination).
25. Infectious agent
An organism (virus, rickettsia, bacteria, fungus, protozoan or
helminth) that is capable of producing infection or infectious disease.
Infectivity expresses the ability of the disease agent to enter, survive
and multiply in the host; infectiousness indicates the relative ease with
which a disease is transmitted to other hosts.
26. Infectious disease
A clinically manifest disease of humans or animals resulting from a
infection. (See Infection).
27. Infestation
For persons or animals, the lodgment, development and reproduction of
arthropods on the surface of the body or in the clothing. Infested
articles or premises are those that harbor or give shelter to animal forms,
especially arthropods and rodents.
28. Insecticide
Any chemical substance used for the destruction of insects, whether
applied as powder, liquid, atomized liquid, aerosol or “paint” spray;
residual action is usual. The term larvicide is generally used to
designate insecticides applied specifically for destruction of immature
stages of arthropods; adulticide or imagocide, to designate those applied
to destroy mature or adult forms. the term insecticide is often used
broadly to encompass substances for the destruction of all arthropods, but
acaricide is more properly used for agents against ticks and mites. More
specific terms such as lousicide and miticide are sometimes used.
29. Isolation
As applied to patients, isolation represents separation, for the
period of communicability, of infected persons or animals from others in
such places and under such conditions as to prevent or limit the direct or
indirect transmission of the infectious agent from those infected to those
who are susceptible to infection or who may spread the agent to others. In
contrast, quarantine (q.v.) applies to restrictions on the healthy
contacts of an infectious case.
CDC has recommended that Universal Precautions be used consistently for
all patients (in hospital settings as well as outpatient settings)
regardless of their blood borne infection status. this practice is based
on the possibility that blood and certain body fluids (any body secretion
that is obviously bloody, semen, vaginal secretions, tissue, CSF, and
synovial, pleural, peritoneal, pericardial and amniotic fluids) of all
patients are potentially infectious for HIV, HBV and other blood borne
pathogens. Universal precautions are intended to prevent parenteral,
mucous membrane and nonintact skin exposures of healthcare workers to
blood borne pathogens. Protective barriers include gloves, gowns, masks
and protective eyewear or face shields. A private room is indicated if
patient hygiene is poor. Waste management is controlled by local and state
authority.
There are two basic requirements that are common for care of all
potentially infectious cases:
· Hands must be washed after
contact with the patient or potentially contaminated articles and before
taking care of another patient; and
· Articles contaminated with
infectious material should be appropriately discarded or bagged and
labeled before being sent for decontamination and reprocessing.
Recommendations
made for isolation of cases in section 9B2 of each disease may allude to
the methods that had been recommended by CDC (CDC guideline for
isolation Precautions in Hospitals) as category-specific isolation
precautions, in addition to universal precautions, based on the mode of
transmission of the specific disease. These categories are also follows.
1) Strict isolation: this
category is designed to prevent transmission of highly contagious or
virulent infections that may be spread by both air and contact. The
specifications, in addition to those above, include a private room and the
use of masks, gowns and gloves for all persons entering the room. Special
ventilation requirements with the room at negative pressure to surrounding
areas are desirable.
2) Contact isolation: For less
highly transmissible or serious infections, for diseases or conditions
that re spread primarily by close or direct contact. In addition to the
basic requirements, a private room is indicated, but patients infected
with the same pathogen may share a room. Masks are indicated for those who
come close to the patient, gowns are indicated if soiling is likely and
gloves are indicated for touching infectious material.
3) Respiratory isolation: To
prevent transmission of infectious diseases over short distances through
the air, a private room is indicated, but patients infected with the same
organism may share a room. In addition to the basic requirements, masks
are indicated for those who come in close contact with the patient; gowns
and gloves are not indicated.
4) Tuberculosis isolation (AFB
isolation): For patients with pulmonary tuberculosis who have a positive
sputum smear or a chest x-ray that strongly suggests active tuberculosis.
Specifications include use of a private room with special ventilation and
closed door. In addition to the basic requirements, respirator-type masks
are used by those entering the room. Gowns are used to prevent gross
contamination of clothing. Gloves are not indicated.
5) Enteric precautions: For
infections transmitted by direct or indirect contact with feces. In
addition to the basic requirements, specifications include use of a
private room if patient hygiene is poor. Masks are not indicated; gowns
should be used if soiling is likely and gloves are to be used for touching
contaminated materials.
6) Drainage/secretion precautions:
To prevent infections transmitted by direct or indirect contact with
purulent material or drainage from a infected body site. A private room
and masking are not indicated; in addition to the basic requirements, gown
should be used if soiling is likely and gloves should be used for touching
contaminated materials.
30. Molluscicide
A chemical substance used for the destruction of snails and other
molluscs.
31. Morbidity rate
An incidence rate (q.v.) used to include all persons in the population
under consideration who become clinically ill during the period of time
stated. The population may be limited to a specific gender or age group,
or to those with certain other characteristics.
32 Mortality rate
A rate calculated in the same way as an incidence rate (q.v.) by
dividing the number of deaths occurring in the population during the
stated period of time, usually a year, by the number of persons at risk of
dying during the period. A total or crude mortality rate utilizes deaths
from all causes, usually expressed as deaths per 1’000. A
disease-specific mortality rate covers deaths due to only one disease and
is often reported on the basis of 100’000 persons. the population base
may be defined by gender, age or other characteristics. The mortality rate
must not be confused with case-fatality rate (q.v.). Synonym: death rate).
33. Nosocomial infection
An infection occurring in a patient in a hospital or other healthcare
facility in whom it was not present or incubating at the time of admission;
or the residual of an infection acquired during a previous admission.
Includes infections acquired in the hospital but appearing after discharge,
and also such infections among the staff of the facility. (Synonym:
hospital-acquired infection).
34. Pathogenicity
The property of an infectious agent that determines the extent to
which overt disease is produced in an infected population, or the power of
an organism to produce disease.
35. Patient or sick person
A person who is ill.
36. Personal hygiene
In the field of infectious disease control, those protective measures,
primarily within the responsibility of the individual, that promote health
and limit the spread of infectious diseases, chiefly those transmitted by
direct contact. Such measures encompass (1) washing hands in soap and
water immediately after evacuating bowel or bladder and always before
handling food or eating; (2) keeping hands and unclean articles, or
articles that have been used for toilet purposes by others, away from the
mouth, nose, eyes, ears genitalia and wounds; (3) avoiding the use of
common or unclean eating utensils, drinking cups, towels, handkerchiefs,
combs, hairbrushes and pipes; (4) avoiding exposure of other persons to
spray from the nose and mouth as in coughing, sneezing, laughing or
talking; (5) washing hands thoroughly after handling a patient or the
patient’s belongings; and (6) keeping the body clean by frequent soap
and water baths.
37. Prevalence rate
The total number of persons sick or portraying a certain condition in
a stated population at a particular time (point prevalence), or during a
stated period of time (period prevalence), regardless of when that illness
or condition began, divided by the population at risk of having the
disease or condition at the point in time or midway through the period in
which they occurred.
38. Quarantine
Restriction of the activities of well persons or animals who have been
exposed to a case of communicable disease during its period of
communicability (i.e., contacts) to prevent disease transmission during
the incubation period if infection should occur.
39. Repellent
A chemical applied to the skin or clothing or other places to
discourage (1) arthropods from alighting on and attacking an individual,
or (2) other agents, such as helminthes larvae, from penetrating the skin.
40. Report of a disease
An official report notifying an appropriate authority of the
occurrence of a specified communicable or other disease in humans or in
animals. Diseases in humans are reported to the local health authority;
those in animals, to the livestock, sanitary, veterinary or agriculture
authority. Some few diseases in animals, also transmissible to humans, are
reportable to both authorities. Each health jurisdiction declares a list
of reportable diseases appropriate to its particular needs (see
Communicable Disease Reporting). Reports should also list suspected cases
of diseases of particular public health importance, ordinarily those
requiring epidemiologic investigation or initiation of special control
measures.
When a person is infected in one health jurisdiction and the case
is reported from another, the health authority receiving the report should
notify the jurisdiction where infection presumably occurred, especially
when the disease requires examination of contacts for infection, or if
food, water or other common vehicles of infection may be involved.
In
addition to routine report of cases of specified diseases, special
notification is required of all epidemics or outbreaks of disease,
including diseases not listed as reportable. (See Epidemic). Special
reporting requirements specified in International Health Regulations are
presented in Communicable Disease Reporting.
41. Reservoir (of infectious agents)
Any person, animal, arthropod, plant, soil or substance (or combination of
these) in which an infectious agent normally lives and multiplies, on
which it depends primarily for survival, and where it reproduces itself in
such manner that it can be transmitted to a susceptible host.
42. Resistance
The sum total of body mechanisms that interpose barriers to the
invasion or multiplication of infectious agents, or to damage by their
toxic products. Inherent
resistance – an ability to resist disease independent of immunity or of
specifically developed tissue responses; it commonly resides in anatomic
or physiologic characteristics of the host and may be genetic or acquired,
permanent or temporary. (See Immunity). (Synonym: Nonspecific immunity).
43. Rodenticide
A chemical substance used for the destruction of rodents, generally
through ingestion. (See Fumigation).
44. Source of infection
The person, animal,
object or substance from which an infectious agent passes to a host.
Source of infection should be clearly distinguished from source of
contamination, such as overflow of a septic tank contaminating a water
supply, or an infected cook contaminating a salad. (See Reservoir).
45. Surveillance of disease
As distinct from surveillance of persons (see Quarantine, 2), Surveillance
of disease is the continuing scrutiny of all aspects of occurrence and
spread of a disease that are pertinent to effective control. Included are
the systematic collection and evaluation of
1) morbidity and mortality
reports;
2) special reports of field
investigations of epidemics and of individual cases;
3) isolation and identification
of infectious agents by laboratories;
4) data concerning the
availability, use and untoward effects of vaccines and toxoids, immune
globulins, insecticides and other substances used in control;
5) information regarding immunity
levels in segments of the population; and
6) other relevant epidemiologic
data. A report summarizing the above data should be prepared and
distributed to all cooperating persons and others with a need to know the
results of the surveillance activities.
The procedure applies to all jurisdictional levels of
public health from local to international. Serologic surveillance
identifies patterns of current and past infection using serologic tests.
46. Susceptible
A person or animal not possessing sufficient resistance against a
particular pathogenic agent to prevent contracting infection or disease
when exposed to the agent.
47. Suspect
In infectious disease control, illness in a person whose history and
symptoms suggest that he or she may have or be developing a communicable
disease.
48. Transmission of infectious agents
Any mechanism by which an infectious agent is spread from a source or
reservoir to a person. These mechanisms are as follows.
1) Direct transmission: Direct
and essentially immediate transfer of infectious agents to a receptive
portal of entry trough which human or animal infection may take place.
This may be by direct contact such as touching, biting, kissing or sexual
intercourse, or by the direct projection (droplet spread) of droplet spray
onto the conjunctiva or onto the mucous membranes of the eye, nose or
mouth during sneezing, coughing, spitting, singing or talking (usually
limited to a distance of about 1 m or less).
2) Indirect transmission:
a) Vehicle-borne: Contaminated
inanimate materials or objects (fomites) such as toys, handkerchiefs,
soiled clothes, bedding, cooking or eating utensils, surgical instruments
or dressing; water, food, milk, and biological products including blood,
serum, plasma, tissues or organs; or any substance serving as an
intermediate means by which an infectious agent is transported and
introduced into a susceptible host through a suitable portal of entry. the
agent may or may not have multiplied or developed in or on the vehicle
before being transmitted.
b) Vector-borne: (i) Mechanical:
Includes simple mechanical carriage by a crawling or flying insect through
soiling of its feet or proboscis, or by passage of organisms through its
gastrointestinal tract. This does not require multiplication or
development of the organism. (ii) Biological: Propagation (multiplication),
cyclic development, or a combination of these (cyclopropagative) is
required before the arthropod can transmit the infective form of the agent
to humans. An incubation period (extrinsic) is required following
infection before the arthropod becomes infective. The infectious agent may
be passed vertically to succeeding generations (transovarian transmission);
transstadial transmission indicates its passage from one stage of life
cycle to another, as nymph to adult. Transmission may be by injection of
salivary gland fluid during biting, or by regurgitation or deposition on
the skin of feces or other material capable of penetrating through the
bite sound or through an area of trauma from scratching or rubbing. This
transmission is by an infected nonvertebrate host and not simple
mechanical carriage by a vector as a vehicle. however, an arthropod in
either role is termed a vector.
3) Airborne: the dissemination of
microbial aerosols to a suitable portal of entry, usually the respiratory
tract. Microbial aerosols are suspensions of particles in the air
consisting partially or wholly of microorganisms. They may remain
suspended in the air for long periods of time, some retaining and others
losing infectivity or virulence. Particles in the 1 to 5 mm range are easily drawn into the alveoli of the lungs and may be
retained there. Not considered as airborne are droplets and other large
particles that promptly settle out (see Direct transmission, above).
a) Droplet nuclei: Usually the
small residues that result from evaporation of fluid from droplets emitted
by an infected host (see above). They may also be created purposely by a
variety of atomizing devices, or accidentally as in microbiology
laboratories or in abattoirs, rendering plants or autopsy rooms. They
usually remain suspended in the air for long periods of time.
b) Dust: The small particles of
widely varying size that may arise from soil (as, e.g., fungus spores
separated from dry soil by wind or mechanical agitation), clothes, bedding
or contaminated floors.
49. Universal precautions
See under Isolation, Universal blood/body fluid precautions.
50. Virulence
The degree of pathogenicity of an infectious agent, indicated by
case-fatality rates and/or the ability of the agent to invade and damage
tissues of the host.
51. Zoonosis
an infection or infectious disease transmissible under natural
conditions from vertebrate animals to humans. May be enzootic or epizootic.
(See endemic and Epidemic).
|