Type of Infections, Host, Reservoir & Carriers of Infectious agents

Table of Contents

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