Definitions of communicable diseases dr.wah

1. Definitions of Communicable Diseases
Dr. Win Aye Hlaing
Lecturer
Department of Epidemiology
University of Public Health, Yangon
Monday, June 26, 2017 1

2. DEFINITIONS IN COMMUNICABLE DISEASE
1. Communicable disease
An illness due to a specific infectious agent or its toxic
products that arise through transmission of that agent or
its products from an infected person animal or inanimate
reservoir to a susceptible host either directly or indirectly
(synonym: Infectious disease)
2. Communicable period
The time during which an infectious agent may transfer
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

3. 3. Infection
The entry, lodgment, development and/or
multiplication of an infectious agent in the host. It is
not equivalent to infectious disease. The result may be
in-apparent or manifest. (not synonym with
contamination or infestation)
4. Contamination
The presence of infectious agent on a body surface, or
in clothes, bedding, toys, surgical instruments or
dressings or other inanimate articles or substances
including water, milk and food
5. Infestation
Lodgment, development and reproduction of
arthropods on the surface of the body or in clothing.
e.g. Lice, itch, mite and parasitic worms (Ascariasis)

4. 6. Infectious disease
A clinically manifest disease of man or animals
resulting from an infection
7. Contagious disease
A disease that is transmitted through contact. E.g.
Scabies, Trachoma, STD, Leprosy, etc.
8. Exotic
Disease, which are imported into a country in
which they do not otherwise occur (E.g. rabies in
United Kingdom)
9. Sporadic - Irregularly and infrequently occurred
cases, it may be a starting point of an epidemic

5. 10. Endemic disease
The constant presence of a disease or infectious agent
within a given geographical area or population group.
Hyperendemic represent a constant presence with relative high
incidence [ with relatively high prevalence and incidence rates
(Enzootic) ]
11. Outbreak
Occurrence of more cases of disease than expected, in a
given area, among a specific group of people, over a particular
period of time.
12. Epidemic disease
The occurrence in a community or region of cases of an
illness (or an outbreak ) clear in excess of normal expectancy
(Epizootic)
13. Pandemic
An epidemic affecting a large proportion of the population.
E.g. the entire nation, a continent or the world

6. 14. Incubation period
The time interval between invasion by an
infectious agent and appearance of the first
symptom or sign of a disease
15. Latent period
Incubation period of non-infectious diseases is
called latent period. It is the time interval
between the initiations of a disease to
detection of a disease

7. 16. Pathogenicity
The ability to produce overt disease, which is
measured by the ratio of number of persons
developed illness to the number exposed to
infection
17. Virulence
A measure of the severity of disease or the
degree of pathogenecity of an infectious agent. It
varies from very low to very high. Indicate by CFR
or the ability of the agent to invade and damage
tissues of the host

8. 18. Agent
A substance, living or non-living, or a force, tangible or
intangible, the excessive presence or relative lack of
which may initiate or perpetuate a disease process. A
disease may have a single, multiple or combined and
complex agents
19. Reservoir
Any person, animal, arthropod, plant or an
environmental source (or combination of these) in
which an infectious agent normally live or multiply, on
which it depends primary for survival, and which it
reproduces itself in such manner that it can be
transmitted to a susceptible host

9. 20. Source
The person, animal or object from which an
infectious agent passes to a host.( Distinct
from source of contamination)
21. Sources of infection
The places from which an infectious agent
passes immediately to a susceptible host

10. 22. Notification
Immediate intimation of the occurrence of a
communicable disease by a responsible person to
the local health authorities to take immediate
action to prevent spread of disease
23. Reporting
The reporting of occurrence of communicable
disease by the local health personal to his higher
authority (HA-TMO-DHO-DG-Minister of Health-
WHO)
24. Susceptible person
A person or animal not possessing sufficient
resistance to prevent contracting the infection or
disease when exposed to an agent

11. 25. Isolation
The separation for the period of communicability, of
infected persons or animals from others, in such place
and under such conditions as to prevent the direct or
indirect conveyance of the infectious agent from those
infected to those who are susceptible or who may
spread the agent to others
26. Quarantine
Restriction of the movements or activities of a well
individual or animal who has been exposed to a
communicable disease during the period of
communicability of that disease and in such a manner
that transmission of the disease should have occurred.
The duration of the quarantine ordered shall be
equivalent to the usual incubation period of the
disease to which the susceptible person or animal was
exposed

12. Monday, June 26, 2017 12
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