APPLICATIONS OF EPIDEMIOLOGY IN COMMUNITY HEALTH
What is Epidemiology?

It is the study of the distribution and determinants of health-related states or
events in specified populations, and the application of this study to the
prevention and control of health problems
TERM
EXPLANATION
Study
Includes surveillance, observation, hypothesis testing, analytic
research, and experiments
Distribution
Refers to analysis by time, places, and classes of people affected
Determinants
Include all the biological, chemical, physical, social, cultural,
economic, genetic, and behavioral factors that influence health
Health-related states
or events
Refer to diseases, causes of death, behaviors such as the use of
tobacco, positive health states, reactions to preventive regimens
and, provision and use of health services
Specified populations
Include those with identifiable characteristics such as occupational
groups
Application to
prevention and
control
The aim of PH – to promote, protect, and restore good health
Epidemiology makes use of concepts and methods from fields of :

Biology - uses molecular or genetic markers to trace the development of a disease in a
population, and to understabd trans,mission as well as the population structure and evolution of
pathogens

Sociology - is the study of human society, its origins, functions, and problems. It focuses on
relations among people, groups, classes, organizations, and cultures.

Demography - the study of human populations (size, structure, and development)

Geography - the study of places and the relationships between people and their environments.

Environmental science

Policy analysis

Statistics
TERMINOLOGIES:
Cases - people afflicted with a disease
Epidemic - an unexpectedly large number of cases of disease in a particular population;
disease occurrence in excess of normal expectancy (An outbreak of disease that attacks many
peoples at about the same time and may spread through one or several communities.)
Endemic - a disease that occurs regularly in a population as a matter of course; normally
prevails in the community (a disease that exists permanently in a particular region or population.
Malaria is a constant worry in parts of Africa.)
Hyperendemic - persistent, high levels of disease occurrence
Pandemic - an outbreak of disease over a wide geographical area such as a continent
(When an epidemic spreads throughout the world)
Sporadic Disease - few scattered cases
Practical Applications of Epidemiology
1. Assessment of the health status of the community or community diagnosis
2. Elucidation of the natural history of disease
3. Determination of disease causation
4. Prevention and control of disease
5. Monitoring and evaluation of health interventions
6. Provision of evidence for policy formulation
DISEASE - An abnormal condition of an organism or part, especially as a
consequence of an infection, inherent weakness or environment stress, that
impairs physiological functioning.
Literally, the opposite of ease, when something is wrong with a bodily function.
Disease, Illness, and Sickness
According to M.W. Susser,
DISEASE - is a physiological or psychological dysfunction; is defined as a
condition that is diagnosed by a physician or other medical expert. Ideally, this
would include a specific diagnosis according to standardized and systematic
diagnostic codes.
ILLNESS - a subjective state of the person who feels aware of not being well; is
often based on self reported mental or physical symptoms. In some cases this
may mean only minor or temporary problems, but in other cases self reported
illness might include severe health problems or acute suffering. It may include
health conditions that limit the person’s ability to lead a normal life.
SICKNESS - a state of social dysfunction , i.e. a role that the individual assumes
when ill; is related to a different phenomenon, namely the social role a person
with illness or sickness takes or is given in society, in different arenas of life. One
type of data concerning a more limited aspect of sickness is that relating to
sickness absence from work.
DISEASE AND EXPOSURE
DISEASE - A broad array of health conditions that we seek to understand and
ultimately modify, including the physiologic states, mental health, and the entire
spectrum of human diseases

outcome variable (dependent variable)
EXPOSURE - A catch-all term for agents, interventions, conditions, policies, and
anything that might affect health

predictor / explanatory variable (independent variable)
COMPONENTS OF EPIDEMIOLOGY:
1. Studies of disease frequency - Measurement of frequency of disease,
disability, death


Prevalence is a statistical concept referring to the number of cases of a
disease that are present in a particular population at a given time (old
and new cases)

Incidence refers to the number of new cases that develop in a given
period of time

May yield important clues to disease etiology and development of
strategies for disease prevention and control
2. Studies of disease distribution - Characterize who, where, or when in
relation to what (outcome)

Person: characteristics (age, sex, occupation) of the individuals
affected by the outcome

Place: geography (residence, work, hospital) of the affected
individuals

Time: when events (diagnosis, reporting, testing) occurred

“Descriptive epidemiology”

Generate hypothesis
Hypothesis – an idea or theory that is not proven but that leads to further study or
discussion; a tentative assumption made in order to draw out and test its logical or
empirical consequences.
3. Studies of determinants of disease

Test hypothesis

Answer why and how

“Analytical epidemiology”

Help in development of health programs, interventions, and policies
AREAS OF CONCERN OF EPIDEMIOLOGY
1. Describing the distribution of disease in terms of sex, age, race, geography,
etc.
2. Interpretation of the distribution of the disease in terms of possible
etiologic agent of causal factors.
SCOPE OF EPIDEMIOLOGY
1. To trace the source of epidemic
2. Limit the spread
3. Institute control measures
4. Prevent similar occurrence in the future
ULTIMATE CONCERN OF EPIDEMIOLOGY
1. Prevention of diseases
2. Maintenance of health
PH IMPORTANCE OF EPIDEMIOLOGY

It provides framework for different approaches for control measures.
ASSESSMENT OF THE HEALTH STATUS OF THE COMMUNITY (Community
Diagnosis)
 Epidemiology is often used to describe the health status of the population
through estimation of health indicators.
 Health indicators � are quantitative measures that describe and summarize
various aspects of the health status of the population.
Other uses of health indicators (Turnock, 2007):
1. Determining factors that may contribute to causation and control of diseases.
2. Identifying public health problems and needs.
3. Indicating priorities for resource allocation.
4. Monitoring implementation of health programs.
5. Evaluating outcomes of health programs.
Types of Health Indicators:

Health status indicators (Morbidity/Mortality)

Population indicators - age-sex structure of the pop, pop density, pop
growth indicators(CBR, fertility rate)

Indicators for the provision of health care - access to health programs or
facilities; availability of health resources

Risk reduction indicators - % of cases consulting a health provider, % of
infants exclusively breastfed for the first 6 mos, no. of children fully
vaccinated

Social and economic indicators -types and levels of employment, availability
of housing, no. of persons per room, availability and distribution of food
supplies

Environmental indicators

Disability indicators - indicators of restricted activity (bed-disability days,
work loss days), indicators of long-term disability (chronic activity
limitation)

Health policy indicators - collaboration between govt and NGOs, equity in
the distribution of resources, AVAILABAILITY OF A PUBLIC POLICY
STATEMENT AND HEALTH PLAN
STAGES IN THE NATURAL HISTORY OF DISEASE AND THE LEVELS OF
PREVENTION
l. Stage of susceptibility (Prepathogenesis stage)

The person is not yet sick but may be exposed to the risk factors of the
disease

E.g. multiple sex partners in the case of cervical cancer.

Primary level of prevention refers to those activities that are undertaken to
prevent the disease and injury from occurring (HEALTH PROMOTION &
HEALTH PROTECTION ACTTIVITIES)

such as health education and immunization
ll. Stage of subclinical disease
The person is still apparently healthy since clinical manifestations of the disease
are not yet shown, although pathologic changes have already occurred.
Secondary level of prevention is the early diagnosis and management to prevent
complications from a disease. (Use of lab. Procedures, examination of contacts,
use of consultant/specialist in CDs)

like Pap smear
lll. Stage of clinical disease
The patient now manifests recognizable signs and symptoms, for example, vaginal
bleeding.
Tertiary levels of prevention - involves activities directed at the host in order to
promote rehabilitation, restoration, and maintenance of maximum function after
the disease and its complications have stabilized.
lV. Stage of Recovery, Disability or Death

The patient either recovers completely from the disease, becomes a
chronic case, with, or without disability, or dies.
Natural history of disease refers to the progression of a disease process in an
individual over time, in the absence of treatment.
The onset of symptoms marks the transition from subclinical to clinical
disease. Most diagnoses are made during the stage of clinical disease.
Ultimately, the disease process ends either in recovery, disability or death.
The onset of symptoms marks the transition from subclinical to clinical disease.
Most diagnoses are made during the stage of clinical disease.
Ultimately, the disease process ends either in recovery, disability or death.
DETERMINATION OF DISEASE CAUSATION

Interventions that target the causes of a public health problem have
greater chances of having positive outcomes, hence the need to determine
the etiology of the disease.

“What factors contribute to disease causation?”

“Why does disease occur?”
MODELS OF DISEASE CAUSATION
The model suggest that the agent and the susceptible/vulnerable human host are
interacting freely in a common environment.
AGENT: or microbe that causes the disease (“what”)
HOST: or organism (human/animals) harboring the disease (“who”)
ENVIRONMENT: or those external factors that cause or allow disease
transmission(“where”)
- physical factors such as geology, climate, and physical surroundings (e.g., a
nursing home, hospital)
- biologic factors (insects that transmit the agent)
- socioeconomic factors (crowding, sanitation, availability of health services)
For as long as the balance is maintained or is tilted in favor of the host (because of
good nutritional status and high levels of immunity), disease does not occur.
When the balance is tilted in favor of the agent (thru increased dosage, virulence,
pathogenicity of the agent), disease eventually occurs.
Pathogenicity refers to the ability of an organism to cause disease
Virulence – quantitative measure of the degree of pathogenicity of a particular
microorganism
The model gives emphasis on the role of the genetic make up of the host that is
presented as the inner core of the wheel’s hub. The outer core of the hub
includes host characteristics like sex, age, SES, and behaviors. The rim or the outer
edge represents the biologic, physical, and chemical environment.
This is deemed applicable to use for NCDs inorder to capture the complex
interrelationships of numerous factors.
PREVENTION, INTERVENTION, CONTROL, AND ERADICATION OF DISEASES
Prevention: the planning for and taking of action to forestall the onset of a
disease or other health problem
Intervention: is a combination of program elements or strategies designed to
produce behavior changes or improve health status among individuals or an
entire population.

efforts to control a disease in progress
Control: various measures that prevent and contain the spread of infectious dse
(Hand washing, infection control std, contact, droplet and airborne
precautions,control of vectors of infection)

the limiting of transmission of a communicable disease in a population
Eradication: the complete elimination or uprooting of a disease
OUTBREAK INVESTIGATION :
Disease outbreak

the occurrence of cases of disease in excess of what would normally be
expected in a defined community, geographical area or season (WHO,2012)

an occurrence of one case of a CD is considered an outbreak provided the
disease is either a previously unknown disease , has never occurred in the
area where the lone case is observed, or has never been absent from the
population for a long time
Basic Steps in an Outbreak Investigation
1. Operationally, define what constitutes a case.
2. Based on the operational definition, identify the cases.
3. Based on the number of identified cases, verify the existence of an outbreak.
4. Establish the descriptive epidemiologic features of the cases.
5. Record the clinical manifestations of cases.
6. Formulate a hypothesis regarding the probable etiologic agent, the sources of
infection, the MOT, and the best approach for controlling the outbreak.
7. Test the hypothesis by collecting relevant specimens from the patients and
from the environment.
8. Implement prevention and control measures to prevent recurrence of a similar
outbreak.
9. Disseminate the findings of the investigation through media and other forms
to inform the public.
MONITORING AND EVALUTION OF HEALTH INTERVENTIONS
Monitoring

is an ongoing activity during the program implementation to assess the
current status of its implementation in terms of compliance to the design of
the program, timeliness, and attainment of goals (Kettner et al.,1999)
As a result of monitoring, the project management team is able to:

Assess the progress of program implementation.

Identify problems.

Take corrective action.

Have a tool for quality assurance and management.

Measure achievement of program objectives.

Lay the groundwork for program evaluation.
Evaluation

is a process that systematically and objectively assesses compliance to the
design of the program, the performance, the relevance and success of a
project, that is, the extent to which a project accomplishes its goals and
achieves measurable impacts.
“Did the program work as intended?”
EPIDEMIOLOGIST VS PHYSICIAN
Epidemiologist
Physician
Differences
Patients are whole community during
Patient – individual during illness
Epidemic, endemic and pandemic
Similarities but differ in methodology and technology
 Diagnose patient using
 Diagnose patient using
observational epidemiology,
stethoscope, BP apparatus, XNatural experimentation
ray, Laboratory, etc…
Epidemiology, and Theoretical
Epidemiology
Treatment:
Treatment :
 Preventive and control
 Using medicines, surgery, etc…
measures of the community
Diag