INTRODUCTION TO COMMUNICABLE DISEASES IN ENGLISH
watch my youtube video to understand this topic in easy way-
https://www.youtube.com/watch?v=sGn3dvpUWzk
COMMUNICABLE
DISEASES-
DYNAMICS OF
COMMUNICABLE DISEASES-
Ø To complete the process of disease
transmission it needs six links. These are known as chain of infection. These
links are-
Ø Infectious agent,
Ø source or reservoir,
Ø portal of exit,
Ø mode of transmission,
Ø portal of entry and
Ø susceptible host.
Ø Infectious agent-The first link in the chain of disease
transmission is an infectious agent. The disease "agent" is defined
as a the presence of which may initiate
the disease process. Infectious agent may be
bacteria, viruses, fungi or parasites.
Ø source or reservoir- The source is defined as the person/
animal/object or substance from which and infectious agent passes to the host.
Reservoir is defined as the person/ animal/object or substance in which the
infectious agent live and multiply before passing the susceptible host.
Ø The terms reservoir and source are not
always interchangeable. For example, in hookworm infection, the reservoir is
man, but the source of infection is the soil contaminated with infective
larvae.
Ø Reservoir may be human reservoir (case or
carrier) Animal reservoir (animal and birds) and nonliving reservoir such as
soil.
Ø A case is defined as "a person
identified as having the particular disease, health disorder or condition” In
other words we can say that a patient is known as a case.
Ø A carrier is defined as "an infected
person or animal that harbours a specific infectious agent in the absence of
clinical disease and serves as a potential source of infection for others.
Ø portal of exit-Portal of exit is the path by which a infectious agent
leaves its host. The portal of exit usually corresponds to the site where the
pathogen is localized. For example, influenza viruses and bacteria Mycobacterium
tuberculosis exit the respiratory tract.
Ø mode of transmission- Mode of transmissions are the different
ways by which infectious agent is transmitted to the host and infect the new
host. It is classified as-
Ø Direct
transmission and
Ø Indirect
transmission.
Ø Direct
transmission - when infectious agent is directly transferred from
source/reservoir to host than it is known as direct transmission. It includes
direct contact, droplet infection, contact with soil, inoculation into skin and
trans placental transmission.
Ø Indirect
transmission - when infectious agent is not directly transferred from
source to host than it is known as indirect transmission. It includes vehicle
borne infection such as water borne,
food borne, milk borne, blood borne etc.
vector born infection such as through mosquito or flys, fomite born infection and infection through
contaminated hand and fingers.
Ø portal of entry- The portal of entry refers to the manner in which a
pathogen enters a susceptible host. The portal of entry must provide access to
tissues in which the pathogen can multiply or a toxin can act. Often,
infectious agents use the same portal to enter a new host that they used to
exit the source host. For example, influenza virus exits the respiratory tract
of the reservoir and enters through the
respiratory tract of the new host.
Ø susceptible host-The final link in the chain of infection is
a susceptible host. He is a person who is susceptible or at risk to get
infection. Susceptibility of a host depends on specific immunity, and
nonspecific factors that affect an individual’s ability to resist infection or
having unprotected exposure.
No comments:
Post a Comment