Important Term & Definition
A. Infectious agent:
A microorganism which is capable of producing an infection. (bacteria, virus, fungi, parasite and prion)
B. Infection:
Invasion of the body tissue of a host by an infectious agent whether or not it causes disease
Pathogenicity: refer to the ability of microbial species to produce disease
Virulence is the ability of strain of microorganisms to cause disease. M. Tuberculosis contain strain of a varying degree of virulence. Eg. The vaccine contains avirulent strain.
o Virulence of a strain is not constant and may undergo variation
o Exaltation: enhancement of virulence of the strain of Microorganism
o Attenuation: reduction of virulence of a strain
Invasiveness: the ability of an organism to spread within the host tissue after establishing infection.
Type of infection
o Primary infection: initial infection
o Reinfection: subsequent infection with the same parasite in the same host
o Secondary infection: when the body resistance is lower by preexisting infectious disease, a new parasite set up an infection secondary infection
o Cross infection: when a patient already suffering from a disease acquires a new infection from another host for another external source. Ex Nosocominal infection
o Iatrogenic infection: Physician induced infection resulting from drug therapy or an investigative procedure(infection like AIDS and Hepatitis B may sometimes transmitted during procedure such as injection, blood transfusion, dialysis and surgery)
o Subclinical infection: when clinical symptoms of infection are not Apparent
o Latent infection: following infection, some parasites may remain in a latent for hidden from in host tissue and they proliferate and produce disease when the resistance of the host is lowered
Atypical infection: Atypical or characteristic clinical manifestations of the infectious disease are not present.
C. Infectious disease:
A disorder caused by an infectious agent/organism
D. Infestation :
Invasion of insect and worm that causes a disease to the host. Eg. Mites, ticks, flea, lice & worm
a. Ectoparasites:
on the surface of host
b. Endoparasite:
inside the host/ lumen of host
E. Contagious disease:
diseases which are transmitted from one person to another person either by direct contact or by casual contact with their secretion / object touched by them
F.Communicable diseases:
disease which are transmitted by direct and indirect (disease is spread from one person to another through a variety of ways)
G. Endemic (स्थानिक):
a disease that exist in a particular/ restricted reason/ area for population with relative Ni low level throughout the year
H. Epidemic (महामारी):
quick and Rapid breathing of infectious disease on a mass scale
I. Pandemic:
Global disease outbreak/ several countries/worldwide
J. Exotic:
a disease which is introduced from a foreign land
K. Nosocomial infection:
infection acquired in Healthcare facility including Hospital biomedical intervention are called nosocomial infection or Healthcare-associated infection (HAI) { acquired as clinical setting}
Example urinary tract infection &upper respiratory tract infection
L. Host (get the disease):
a person or other(but on the living) organism that is susceptible to or harbors an infectious agent under natural condition
a. Primary host: the host in which parasite residues to sexual maturity/ primary host provides food shelter etc
b. Intermediate host: parasite friends only part of its life cycle or does not reach sexual maturity
M. Reservoir
(may be living or non-living): Reservoir of an infectious agent is the habitat in which agents normally live, grows and multiplies to persist over a long period of time &May or may not show effect of illness
Eg: environment (water, Soil, plant), human and animal
N. Carriers:
an individual capable of transmitting pathogen/ agent without display symptoms is referred to as a carrier:
a. Passive carriers: contaminated with agent & can mechanically transmit it to other post (the passive carrier is not infected)
b. Active carriers: infected individual who can transmits disease to others
i. Incubatory: who can transmit the agent during the incubation before clinical illness begins
ii. Convalescent: record from their illness but remain capable of transmitting to others
iii. Chronic: who continue to herbers agent/pathogen surcharge hepatitis B &Salmonella typhi