UNIVERSIDAD DE ZAMBOANGA
MAIN CAMPUS, DON TORIBIO ST., TETUAN, ZAMBOANGA CITY
HEALTH STATISTICS AND EPIDEMIOLOGY
A. Tools
1. Demography
 The science which deals with the study of the human population’s size, composition, and
distribution in space as affected by births, deaths and migration.
 The science of population helps the nurse find reasons or rationale why or how a particular
population or group is influenced by a variety of factors resulting in vulnerability to diseases.
▪ Sources of Data
a. CENSUS- complete enumeration of the population; information about 100% of the population.
2 Ways of Assigning People
 De jure - people were assigned to the place where they usually live regardless of where
they are at the time of census
 De facto - people were assigned to the place where they are physically present at the
time of census, regardless of their usual place of residence.
b. SAMPLE SURVEYS- collected demographic information from a sample of a given population.
c. REGISTRATION SYSTEMS-data collected by the civil registrar’s office which deal with recording
of vital events in the community. Vital events refer to births, deaths, marriages, divorces, and
the likes.
▪ Composition of Demography
a. Population Size
 Refers to the number of people in a given place or area at a given time.
 One method of measuring the population size is by determining the increase in the
population resulting from excess births compared to deaths.
 The second method is to determine the increase in the population using data obtained
during two census periods.
b. Composition - The composition of the population is commonly described in terms of its age
and sex.
 Sex Composition
➢ To describe the sex composition of the population, the nurse computes for the sex
ratio. The sex ratio compares the number of males to the number of females in the
population.
➢ The sex ratio represents the number of males for every 100 females in the
population.
 Age Composition - There are two ways to describe the age composition of the
population:
➢ Median Age
• Age below which 50% of the population fall and above which 50% of the
population fall. The lower the median age, the younger the population (high
fertility, high death rates)
➢ Dependency Ratio
• Compares the number of economically dependent with the economically
productive group in the population.
• The economically dependent are those who belong to the 0-14 and 65 and above
age groups.
• Considered to be economically productive are those within the 15 to 64 age group.
• It represents the number of economically dependent for every 100 economically
productive
 Age and Sex Composition - Can be described at the same time using a population
pyramid. It is a graphical presentation of the age and sex composition of the population.
ELLA B. ALBURO
c. Distribution
 The distribution of the population in space can be described in terms of urban-rural
distribution, population density and crowding index.
 The measures help the nurse decide how meager resources can be justifiably allocated
based on concentration of population in a certain place.
i.
ii.
iii.
Urban-Rural Distribution
• Simply illustrates the proportion of the people living in urban compared to the
rural areas.
Crowding Index
• Describe the ease by which a communicable disease will be transmitted from
one host to another susceptible host.
• This is described by dividing the number of persons in a household with the
number of rooms used by the family for sleeping.
Population Density
• Determine how congested a place is and has implications in terms of the adequacy
of basic health services present in the community. It can be computed by dividing
the number of people living in a given land area.
2. Health Indicators
VITAL STATISTICS
▪ Statistics refers to a systematic approach of obtaining, organizing and analyzing numerical facts
so that conclusion may be drawn from them.
▪ Vital Statistics refers to the systematic study of vital events such as births, illnesses, marriages,
divorce, separation, and deaths.
▪ Statistics of disease (morbidity) and death (mortality) indicate the state of health of a community
and the success or failure of health work.
▪ Statistics on population and the characteristics such as age and sex, distribution are obtained
from the National Statistics Office (NSO).
▪ Births and Deaths are registered in the Office of the Local Civil Registrar of the municipality or
city.
USE OF VITAL STATISTICS:
▪ Indices of the health and illness status of a community.
▪ Serves as bases for planning, implementing, monitoring and evaluating community health nursing
programs and services.
SOURCES OF DATA:
▪ Population census
▪ Registration of Vital data
▪ Health Survey
▪ Studies and researches
RATES AND RATIOS:
RATE - shows the relationship between a vital event and those persons exposed to the occurrence
of said event, within a given area and during a specified unit of time; it is evident that the person
experiencing the event (numerator) must come from the total population exposed to the risk of same
event (denominator).
RATIO - is used to describe the relationship between two numerical quantities or measures of
events without taking particular considerations to the time or place. Theses quantities need not
necessarily represent the same entities, although the unit of measure must be the same for both
numerator and denominator of the ratio.
ELLA B. ALBURO
▪ Crude Birth Rate (CBR)
 A measure of one characteristic of the natural growth or increase in population.

▪ Crude Death Rate

A measure of one mortality
from all causes which may result in a decrease of population.

▪ Infant Mortality Rate
 Measures the risk of dying during the 1st year of life. It is a good index of the general health
condition of a community since it reflects the changes in the environment and medical
condition of a community.

▪ Maternal Mortality
 Measures the risk of dying from causes related to pregnancy, childbirth, and puerperium. It is
an index of the obstetrical care needed and received by women in a community.

▪ Rate Specific Rates of Mortality – describes more accurately the risk of exposure of certain
classes of groups to particular disease.
 Specific Death Rate - Describes more accurately the risk of exposure of certain classes or
groups to particular diseases. To understand the forces of mortality, the rates should be
made specific provided the data are available for both the population and the event in their
specifications. Specific rates render more comparable and thus reveal the problem of public
health.
 Age Specific Death Rate
 Cause Specific Death Rate
▪ Leading Causes of Mortality
1) Heart Diseases
2) Vascular Diseases
3) Pneumonias
4) Malignant Neoplasms/Cancers
5) All forms of Tuberculosis
6) Accidents
7) COPD and allied conditions
8) Diabetes Mellitus
9) Nephritis / Nephritic Syndrome
10)
Other diseases of the Respiratory System
▪ Life Expectancy in the Philippines
 Both sexes: 71.7 years (life expectancy at birth, both sexes combined)
 Female : 75.9 years (life expectancy at birth, females)
 Male: 67.7 years (life expectancy at birth, males)
B. Philippine Health Situation
1. Demographic Profile - Demographic information examples include: age, race, ethnicity, gender,
marital status, income, education, and employment. You can easily and effectively collect these types
of information with survey questions.
▪ The current population of the Philippines is 110,093,359 as of Sunday, November 8, 2020, based
on Worldometer elaboration of the latest United Nations data.
▪ The Philippines 2020 population is estimated at 109,581,078 people at mid year according to UN
data.
▪ The Philippines population is equivalent to 1.41% of the total world population.
ELLA B. ALBURO
▪ The Philippines ranks number 13 in the list of countries (and dependencies) by population.
▪ The population density in the Philippines is 368 per Km2 (952 people per mi2).
▪ The total land area is 298,170 Km2 (115,124 sq. miles)
▪ 47.5 % of the population is urban (52,008,603 people in 2020)
▪ The median age in the Philippines is 25.7 years.
2. Health Profile - the health profile is intended to be a set of indicators of basic demographic and
socioeconomic characteristics, health status, health risk factors, and health resource use, which are
relevant to most communities.
 A community health profile is made up of indicators of sociodemographic characteristics, health
status and quality of life, health risk factors, and health resources that are relevant for most
communities; these indicators provide basic descriptive information that can inform priority
setting and interpretation of data on specific health issues.
 What is typically presented in a community health profile?
 An assessment that covers an entire community will necessarily be broad and include a wide
range of data. A community health profile includes BOTH previously identified health issues
AND the identification of new, emerging issues.
 A comprehensive community health profile includes:
▪ A narrative description of the given community
▪ Community strengths and challenges
▪ Demographic and economic data
▪ Health status data
▪ Community input
▪ Community resources, including services, coalitions, and systems
▪ Interpretation of data presented, from both the perspective of the health council and the
broader community.
▪ COVID-19 REPORT
▪ CASES - 393,961
▪ DEATHS - 7,485
▪ 11/7/20
C. Epidemiology and the Nurse
1. Definitions and Related Terms
EPIDEMIOLOGY
▪ Derived from Greek word “epi” means upon and “demos” means people.
▪ The study of distribution of disease or physiologic condition among human populations and the
factors affecting such distribution.
▪ The study of the occurrence and distribution of health conditions such as disease, death,
deformities or disabilities on human populations.
▪ A medical science that involves the study of the incidence and distribution of diseases in large
populations, and the conditions influencing the spread and severity of disease.
▪ The study of occurrences and distribution of diseases as well as the distribution and determinants
of health states or events in specified population, and the application of this study to the control
of health problems.
CENSUS.
▪ The enumeration of an entire population, usually with details being recorded on residence, age,
sex, occupation, ethnic group, marital status, birth history, and relationship to head of
household.
CHAIN OF INFECTION
▪ A process that begins when an agent leaves its reservoir or host through a portal of exit, and is
conveyed by some mode of transmission, then enters through an appropriate portal of entry to
infect a susceptible host.
DEMOGRAPHIC INFORMATION
▪ The person: characteristics—age, sex, race, and occupation—of descriptive epidemiology used
to characterize the populations at risk.
EPIDEMIOLOGIC TRIAD
▪ The traditional model of infectious disease causation. Includes three components: an external
agent, a susceptible host, and an environment that brings the host and agent together, so that
disease occurs.
HEALTH INDICATOR
ELLA B. ALBURO
▪ A measure that reflects, or indicates, the state of health of persons in a defined population, e.g.,
the infant mortality rate.
IMMUNITY, ACTIVE
▪ Resistance developed in response to stimulus by an antigen (infecting agent or vaccine) and
usually characterized by the presence of antibody produced by the host.
IMMUNITY, PASSIVE
▪ Immunity conferred by an antibody produced in another host and acquired naturally by an
infant from its mother or artificially by administration of an antibody-containing preparation
(antiserum or immune globulin).
2.
USES OF EPIDEMIOLOGY
According to Morris, epidemiology is used to:
▪ Study the history of the health population and the rise and fall of diseases and changes in their
character.
▪ Diagnose the health of the community and the condition of people to measure the distribution
and dimension of illness in terms of incidence, prevalence, disability and mortality, to set health
problems in perspective and to define their relative importance and to identify groups needing
special attention.
▪ Study the work of health services with a view of improving them. Operational research shows
how community expectations can result in the actual provisions of service.
▪ Estimate the risk of disease, defects, and the chances of avoiding them.
▪ Identify syndromes by describing the distribution and association of clinical phenomena in the
population.
▪ Complete the clinical picture of chronic disease and describe their natural history.
▪ Search for causes of health and disease by comparing the experience of groups that are clearly
defined by their composition, inheritance, experience, behavior and environments.
Natural Life History of Disease
 Natural history of disease refers to the progression of a disease process in an individual over time,
in the absence of treatment.
 The process begins with the appropriate exposure to or accumulation of factors sufficient for the
disease process to begin in a susceptible host
 After the disease process has been triggered, pathological changes then occur without the
individual being aware of them. This stage of subclinical disease, extending from the time of
exposure to onset of disease symptoms, is usually called the incubation period for infectious
diseases, and the latency period for chronic diseases.
 During this stage, disease is said to be asymptomatic (no symptoms) or inapparent. This period
may be as brief as seconds for hypersensitivity and toxic reactions to as long as decades for
certain chronic diseases.
 The onset of symptoms marks the transition from subclinical to clinical disease. Most diagnoses
are made during the stage of clinical disease. This range is called the spectrum of disease
3. Epidemiological Triangle
EPIDEMIOLOGIC CONCEPTS AND PRINCIPLES
Multiple Causation Theory or Ecologic Concept of Disease
 Disease development does not rest on a single cause. Health conditions result from a multitude of
factors.
 There are three models that explain the multiple causation theory- the wheel, the web and the ecologic
triad. Of the three, the ecologic triad is most helpful because it highlights not only the host’s and agent’s
roles in disease development but regards the role of the environment as important in disease
causation.
Web of Causation- cause is a condition, reason or ground that plays a significant role in the occurrence of
a disease
 factors that form the WEB CAUSATION – factors are interconnected
▪ microorganisms
▪ genetic abnormalities
▪ socio-economic factors
▪ environmental factors
ELLA B. ALBURO
 the type, duration, rate of exposure to these different factors, the general status of the population and
utilization of health resources can result to different outcomes depending on the manner in which the
individuals and families respond to risk factors and even the disease process itself
THE EPIDEMIOLOGIC TRIANGLE
Host
Agent
Environment
 The model implies that ach must be analyzed and understood for comprehensions and prediction of
patterns of a disease. A change in any of the component will alter an existing equilibrium to increase
or decrease the frequency of the disease.
 It includes the agent causing the problem and the source of infection, including the chain of events and
environmental condition that allowed it to occur.
Agent- The intrinsic property of microorganism to survive and multiply in the environment to produce
disease
Host - Any organism that harbors and provides nourishment for another organism.
Environment - The sum total of all external condition and influences that affects the development of an
organism which can be biological, social, and physical. The environment affects both the agents and
the host.
Three component of the Environment:
▪ Physical environment- is composed of the inanimate surroundings such as the geophysical
conditions of the climate.
▪ Biological environment- makes up the living things around us such as plants and animal life.
▪ Socio-economic environment- may be in the form of level of economic development of the
community, presence of social disruptions and the like.
FACTORS AFFECTING THE DISTRIBUTION OF DISEASES
a) PERSON - Delineation or description of group involved which includes the intrinsic characteristics such
as the age, sex, race, history, habits, socio-economic, occupation and education.
b) PLACE - Geographical distribution in subdivisions of the area affected which includes the extrinsic
factors such as the physical, social, economic and family environment.
c) TIME - A chronological or sequential distribution of onsets of
cases by days, weeks or months
which include the temporal pattern, incubation period, onset and duration of events.
PATTERNS OF DISEASE OCCURRENCE
Epidemic
 a situation when there is a high incidence of new cases of a specific disease in excess of the expected.
 when the proportion of the susceptible are high compared to the proportion of the immunes.
Epidemic Potential
 an area becomes vulnerable to a disease upsurge due to causal factors such as the climatic changes,
ecologic changes, or socio-economic changes.
Endemic
 habitual presence of a disease in a given geographical location accounting for the low number of both
immunes and susceptible, e.g. Malaria is a disease endemic at Palawan
 the causative factor of the disease is constantly available or present to the area.
 constant presence of an event at about the frequency than expected from the past history of the
community.
Sporadic
ELLA B. ALBURO
 disease occurs every now and then affecting only a small number of people relative to the total
population
 presence of occasional cases of the event apparently unrelated in time or space
Pandemic
 global occurrence of a disease
 presence of an event in epidemic proportions, involving many communities and countries in a relatively
short period of time.
LEVELS OF DISEASE PREVENTION:
a) Primary Prevention
 Directed to the healthy population, focusing on prevention of emergence of risk factors (primordial
prevention) and removal of the risk factors or reduction of their levels (specific protection).
 Health promotion activities include provision of proper nutrition, safe water supply and waste
disposal system, vector control, promotion of a healthy lifestyle and good personal habits.
 Specific measures include provision of immunization and prophylaxis to vulnerable or at-risk groups
(e.g. chemoprophylaxis for travelers to malaria endemic areas).
b) Secondary Prevention
 Aims to identify and treat existing health problems at the earliest possible time
 The interventions at this stage can still lead to the control or eradication of the health problem. Such
interventions include screening, case finding, and disease surveillance, prompt and appropriate
treatment.
c) Tertiary Prevention
 It limits the progression of disability. The health care provider attempts to reduce the magnitude or
severity of the residual effects of both infectious diseases and non-communicable ones.
 Day care centers and sheltered workshops are examples of opportunities to achieve the objective
of tertiary prevention in mental illness and drug abuse.
4. Epidemiological Process and Investigations
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
▪ An occurrence of one case of a communicable disease 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 been absent from the population for a long time.
Objectives of Outbreak Investigation:
 Primary- to control the spread of disease
 To determine the causes of disease, its source & mode of transmission
 To determine who is at risk
 To determine what exposures predispose to disease
 To know magnitude of the problem
 To identify new agent
 To determine the effectiveness of control measures
 To identify methods for present & future prevention & control
 Research & training opportunities
 Public, Political and legal concerns
Steps in Outbreak Identification:
i. Operationally define what constitutes a case.
ii. Based on the operational definition, identify the cases.
iii. Based on the number of cases identified, verify the existence of an outbreak.
iv. Established the descriptive epidemiologic features of the cases.
v. Record the clinical manifestation of cases.
vi. Based on the clinical manifestations, incubation period, available laboratory findings, and other
information gathered, formulate a hypothesis regarding the probable etiologic agent, the sources of
infection, the mode of transmission and the best approach for controlling the outbreak.
vii. Test the hypotheses by collecting relevant specimens from the patients and the environment.
viii. Based on the results of the investigation, implement prevention and control measures to prevent
recurrence of a similar outbreak.
ix. Disseminate the findings of the investigation through media and other forms to inform the public.
ELLA B. ALBURO