Unit-2 Social and Preventive Pharmacy Notes BPharmacy 8th semester 2021 Previous Year's Question Papers/Notes Download - HK Technical PGIMS
The aim of preventive medicine is the absence of disease, either by preventing the occurrence of a
disease or by halting a disease and averting resulting complications after its onset. Preventive medicine
can be practiced by governmental agencies, primary care physicians and the individual himself.
Preventive medicine takes a proactive approach to patient care.
Principles of Communicable Diseases Epidemiology
Epidemiology is the study of the distribution and determinants of health-related states and events in
populations, and the application of this study to control health problems
• HOST: Demographic characteristics, Biological characteristics, Socioeconomic
• ENVIRONMENT: Physical environment, Biological environment, Social environment
• AGENTS: Biological agents, Physical agents, Chemical agents, Nutrient agents, Mechanical
agents, Social agents
A communicable disease is an illness due to a specific infectious (biological) agent or its toxic products
capable of being directly or indirectly transmitted from man to man, from animal to man, from animal to
animal, or from the environment (through air, water, food, etc..) to man.
Importance of studying:
1. Changes of the pattern of infectious diseases,
2. Discovery of new infections,
3. the possibility that some chronic diseases have an infective origin
Infection is the entry and development or multiplication of an infectious agent in the body of man or
animals. An infection does not always cause illness. There are several levels of infection (Gradients of
– Colonization (S. aureus in skin and normal nasopharynx)
– Subclinical or in apparent infection (polio)
– Latent infection (virus of herpes simplex)
– Manifest or clinical infection
CONTAMINATION: The presence of an infectious agent on a body surface, on or in clothes, beddings,
toys, surgical instruments or dressings, or other articles or substances including water and food
INFESTATION: It is the lodgment, development and reproduction of arthropods on the surface of the
body or in the clothing, e.g. lice, itch mite. This term could be also used to describe the invasion of the
gut by parasitic worms, e.g. ascariasis.
A contagious disease is the one that is transmitted through contact. Examples include scabies,
trachoma, STD and leprosy.
VECTOR OF INFECTION: An insect or any living carrier that transports an infectious agent from an
infected individual or its wastes to a susceptible individual or its food or immediate surroundings. Both
biological and mechanical transmissions are encountered
HOST: A person or an animal that affords subsistence or lodgment to an infectious agent under natural
conditions. Types include: an obligate host, definitive (primary) host, intermediate host and a transport
RESERVOIR: Any person, animal, arthropod, plant, soil, or substance, or a 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 a manner that it can be transmitted to a susceptible host. It is the
natural habitat of the infectious agent
Incidence of an infectious disease: number of new cases in a given time period expressed as
percent infected per year (cumulative incidence) or number per person time of observation (incidence
Prevalence of an infectious disease: number of cases at a given time expressed as a percent at
a given time. Prevalence is a product of incidence x duration of disease, and is of little interest if an
infectious disease is of short duration (i.e. measles), but may be of interest if an infectious disease is of
long duration (i.e. chronic hepatitis B).
EPIDEMIC: “The unusual occurrence in a community of disease, specific health related behavior, or
other health related events clearly in excess of expected occurrence” (epi= upon; demos= people)
Epidemics can occur upon endemic states too.
ENDEMIC: It refers to the constant presence of a disease or infectious agent within a given geographic
area or population group. It is the usual or expected frequency of disease within a population. (En = in;
demos = people)
The term “hyperendemic” expresses that the disease is constantly present at high incidence and/or
prevalence rate and affects all age groups equally.
The term “holoendemic” expresses a high level of infection beginning early in life and affecting
most of the child population, leading to a state of equilibrium such that the adult population shows
evidence of the disease much less commonly than do the children (e.g. malaria)
PANDEMIC: An epidemic usually affecting a large proportion of the population, occuring over a wide
geographic area such as a section of a nation, the entire nation, a continent or the world, e.g. Influenza
Exotic diseases are those which are imported into a country in which they do not otherwise occur,
as for example, rabies in the UK.
The word sporadic means “scattered about”. The cases occur irregularly, haphazardly from time to
time, and generally infrequently. The cases are few and separated widely in time and place that they
show no or little connection with each other, nor a recognizable common source of infection e.g. polio,
meningococcal meningitis, tetanus….
However, a sporadic disease could be the starting point of an epidemic when the conditions are
favorable for its spread.
Attack rate: proportion of non-immune exposed individuals who become clinically ill.
Primary (index)/secondary cases: The person who comes into and infects a population is the
primary case. Those who subsequently contract the infection are secondary cases. Further spread is
described as "waves" or "generations".
Nosocomial (hospital acquired) infection is an infection originating in a patient while in a
hospital or another health care facility. It has to be a new disorder unrelated to the patient’s primary
condition. Examples include infection of surgical wounds, hepatitis B and urinary tract infections.
Opportunistic infections: This is infection by organisms that take the opportunity provided by a
defect in host defense (e.g. immunity) to infect the host and thus cause disease. For example,
opportunistic infections are very common in AIDS. Organisms include Herpes simplex, cytomegalovirus,
ERADICATION: Termination of all transmission of infection by the extermination of the infectious
agent through surveillance and containment. Eradication is an absolute process, an “all or none”
phenomenon, restricted to termination of infection from the whole world.
ELIMINATION: The term elimination is sometimes used to describe eradication of a disease from a
large geographic region. Disease which are amenable to elimination in the meantime are polio, measles
Reproductive rate of infection: potential for an infectious disease to spread. Influential factors
include the probability of transmission between an infected and a susceptible individual; frequency of
population contact; duration of infection; virulence of the organism and population immune proportion.
A). Source or Reservoir: The starting point for the occurrence of a communicable disease is the
existence of a reservoir or source of infection.
The source of infection is defined as “the person, animal, object or substance from which an infectious
agent passes or is disseminated to the host (immediate source). The reservoir is “any person, animal,
arthropod, plant, soil, or substance, or a 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 a
manner that it can be transmitted to a susceptible host. It is the natural habitat of the infectious agent.”
1. Human Reservoir,
2. Animal reservoir (Rabies, Plague, Bovine TB), also called Zoonosis
3. Non-living reservoir (Soil- tetanus, anthrax etc.)
CASE: A case is defined as “a person in the population or study group identified as having the particular
disease, health disorder, or condition under investigation”
CARRIERS: It occurs either due to inadequate treatment or immune response, the disease agent is
not completely eliminated, leading to a carrier state.
It is “an infected person or animal that harbors a specific infectious agent in the absence of discernible
(visible) clinical disease and serves as a potential source of infection to others.
Three elements have to occur to form a carrier state:
1. The presence in the body of the disease agent.
2. The absence of recognizable symptoms and signs of disease.
3. The shedding of disease agent in the discharge or excretions.
B). Mode of transmission:
DIRECT: Direct contact, Droplet infections, contact with soil, and inoculation into skin of mucosa,
INDIRECT: Vehicle borne, Vector borne (mechanical, biological), Air borne, Fomite born, Unclean hands
C). Susceptible Host:
An infectious agent seeks a susceptible host aiming “successful parasitism”.
Four stages are required for successful parasitism:
1. Portal of entry
2. Site of election inside the body
3. Portal of exit
4. Survival in external environment
Virulence: is the degree of pathogenicity; the disease evoking power of a micro-organism in a given
host. Numerically expressed as the ratio of the number of cases of overt infection to the total number
infected, as determined by immunoassay. When death is the only criterion of severity, this is the case
CASE FATALITY RATE FOR INFECTIOUS DISEASES: is the proportion of infected individuals who die of the
infection. This is a function of the severity of the infection and is heavily influenced by how many mild
cases are not diagnosed.
SERIAL INTERVAL: (the gap in time between the onset of the primary and the secondary cases) the
interval between receipt of infection and maximal infectivity of the host (also called generation time).
INFECTIOUS (COMMUNICABLE) PERIOD: length of time a person can transmit disease (sheds the
INCUBATION PERIOD: time from exposure to development of disease. In other words, the time interval
between invasion by an infectious agent and the appearance of the first sign or symptom of the disease
LATENT PERIOD: the period between exposure and the onset of infectiousness (this may be shorter or
longer than the incubation period).
TRANSMISSION PROBABILITY RATION (TPR):
TPR is a measure of risk transmission from infected to susceptible individuals during a contact.
TPR of differing types of contacts, infectious agents, infection routes and strains can be calculated.
CLASSIFICATIONS OF COMMUNICABLE DISEASES ACCORDING TO NATURE OF THE PATHOGEN
Communicable diseases are classified into nine types according to the nature of the pathogen (causing agent).
1. Viral diseases,
2. Rickettsial diseases,
3. Mycoplasmal diseases,
4. Chlamydial diseases,
5. Bacterial diseases,
6. Spirochaetal diseases,
7. Protozoan diseases, 8. Helminthic diseases and
9. Fungal diseases.
1. Viral Diseases:
1. Poliomyelitis or Polio (Infantile Paralysis):
Enter virus (Poliovirus)
Modes of Transmission:
Polio virus usually enters the body via alimentary canal (faecal oral route) where it multiplies and
reaches the nervous system through the blood stream.
7 to 14 days
Signs and Symptoms:
It produces inflammation of the nervous system. Stiffness of the neck is an important sign. Paralysis
starts following the weakness of particular skeletal muscles. The attack of paralysis begins with high
fever, headache, chilliness, pain all over the body.
Prevention and Treatment:
There must be provided an adequate arrangement for proper disposal of urine and faeces of the patient,
because they contain polio virus. Overcrowding of children in schools, playgrounds and cinema halls
should be avoided. Polio is preventive. Polio vaccine is safe and effective. The first polio vaccine was
prepared by Jonas Salk (1953). The killed virus is called “Salk Vaccine” and injected to develop immunity.
Jonas Salk is called “father of polio vaccine”.
Sabin et al prepared an oral vaccine known as OPV (Oral Polio Vaccine).
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