Transcript ch3 - Health Science

Chapter 3
Practical
Disease
Concepts in
Epidemiology
What Is Disease?
 Disease is an interruption, cessation, or disorder
of body functions, systems, or organs
 Diseases arise from infectious agents, inherent
weaknesses, lifestyle, or environmental stresses
 Environment – all that is external to the human host
(physical, biological, social, cultural, etc.)
Causes of Disease
 Identifying the causes of disease and the
mechanisms by which it spreads remains a
primary focus in epidemiology
 The science and study of the causes of disease
and their mode of operation is referred to as
etiology
Disease Transmission
 The ability of a disease to be transmitted from
one person to another or to spread through the
population is called communicability
Classify acute and chronic diseases
according to infectivity and
communicability
 When an infectious disease is contagious, or
capable of being communicated or transmitted, it
is called a communicable disease
 HIV/AIDS
 Cholera
 Influenza
 Cryptosporidiosis
What are two general types of
disease transmission?
 Vertical transmission – transmission from an
individual to its offspring through sperm,
placenta, milk, or vaginal
 Horizontal transmission – transmission of
infectious agents from an infected individual to a
susceptible contemporary
Pathogens
 Organisms or substances such as prions, bacteria,
viruses, fungi, or parasites that are capable of
producing diseases
 The ability to get into a susceptible host and cause
disease is termed invasiveness
 The disease-evoking power of a pathogen is called
virulence
 Toxins – kill pathogens by poisoning them
 Antibiotics work against pathogens because of
their toxicity
What are two general
classifications of disease?
 Acute – disorder with sudden onset, relatively
severe, and short duration of symptoms
 Chronic – less severe but of long and
continuous duration, lasting over long periods, if
not a lifetime
Questions
 Are all infectious diseases communicable?
 What is an example of a chronic communicable
disease?
 What is an infectious disease that is chronic?
Examples of diseases according to
selected classifications
What are the major stages in the
disease process?
 Stages relevant to most health-related states or
events
1. Stage of susceptibility
2. Stage of pre-symptomatic disease
•
•
Incubation period
Latency period
Stage of clinical disease
4. Stage of recovery, disability, or death
3.
Natural course of communicable
disease
Breaking the Cycle
 Viability – The capacity of the pathogen or
disease-causing agent to survive outside the
host and to exist or thrive in the environment
 Viability – Guinea worm is 1 year
 Solution – Break the cycle for 1 year
What are the five major categories
of disease?
 Congenital and hereditary diseases
 Allergies and inflammatory diseases
 Degenerative diseases
 Metabolic diseases
 Cancer
Congenital and Hereditary Diseases
 Familial tendencies toward certain inborn
abnormalities
 Injury to the embryo or fetus by environmental
factors
 Examples – Down syndrome, hemophilia, heart
disease at an early age
Allergies and Inflammatory Diseases
 Body reacting to an invasion of or injury by a
foreign object or substance
Degenerative Diseases
 Deterioration of body systems, tissue, and
functions
 Often associated with the aging process
Metabolic Diseases
 Cause the dysfunction, poor function, or
malfunction of certain organs or physiological
processes within the body leading to disease
states
 Example – Cells may no longer utilize glucose
normally causing diabetes
Cancer
 Characterized by abnormal growth of cells that
form a variety of tumors, both benign and
malignant
Common modes of entry into the
body of infectious disease agents
 Respiratory
 Oral
 Reproductive
 Intravenous
 Urinary
 Skin
 Gastrointestinal
 Conjunctival
 Transplacental
Zoonosis and Disease in Humans
 Animals can be the host, vector, or source of
certain infections and diseases
 A zoonosis (plural, zoonoses) is an infectious
organism in vertebrate animals (e.g., rabies or
anthrax) that can be transmitted to humans
through direct contact, a fomite, or vector
 The word comes from the Greek words zoon
(animal) and nosos (ill)
Common Zoonotic Diseases
•
•
•
•
•
•
•
•
•
AIDS
Amebiasis
Anthrax
Bovine papular
stomatitis
Brucellosis
California
encephalitis
Cat-scratch fever
Colorado tick
fever
Cowpox
•
•
•
•
•
•
•
•
•
•
•
Dengue fever
Dermatophilosis
Leprosy
Lyme disease
Pasteurellosis
Plague
Q-fever
Rabies
Rat-bite fever
Rickettsialpox
Rocky mountain
spotted fever
• Salmonellosis
• Shigellosis
• Streptococcus
infections
• Tetanus
• Trichinosis
• Tularemia
• Yellow fever
• Zoonotic
scabies
Notifiable Diseases in the United
States
 Notifiable diseases are those of considerable public
health importance because of their seriousness
 Such diseases
 Cause serious morbidity or death
 Have the potential to spread
 Can be controlled with appropriate intervention
Immunity and Immunizations
Against Infectious Diseases
 According to the Centers for Disease Control and
Prevention, if fewer than 80% of the children in a
given area have been inoculated for one of the
contagious diseases, the danger of serious
outbreaks or localized epidemics remains; every
unvaccinated child is at risk.
What Is Active Immunity?
 Active immunity – The body produces its own
antibodies. This can occur through a vaccine or in
response to having a specific disease pathogen
invade the body.
What Is Passive Immunity?
 Passive immunity – acquired through
transplacental transfer of a mother’s immunity to
diseases to the unborn child
Diseases for Which Vaccines
Are Used
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Anthrax
Cervical Cancer (HPV)
Cholera
Chickenpox
Diphtheria
German measles (rubella)
Haemophilus influenzae type b (Hib)
Hepatitis A
Hepatitis B
Influenza
Japanese encephalitis
Lyme disease
Measles
Meningitis
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Mumps
Pertussis
Plague
Pneumonia
Polio
Rabies
Smallpox
Spotted fever
Tetanus
Tuberculosis
Typhoid fever
Typhus
Whooping cough
Yellow fever
What Is Herd Immunity?
 Viewed as the resistance a population has to the
invasion and spread of an infectious disease
 Based on the notion that if a population or group
is mostly protected from a disease by
immunizations (say 80% or more), then the
chance of a major epidemic occurring is highly
limited
Estimated herd immunity thresholds for
vaccine-preventable diseases
Is there a changing emphasis in
epidemiology?
 Increasing life expectancy in modern times and
higher levels of chronic disease has produced a
change in the emphasis of epidemiologic studies
Host-Related Control and Prevention
 Isolation applies to persons who are known to
be ill with a contagious disease. It is often
conducted on an inpatient basis in hospitals or
nursing homes. Most state laws, as well as
accrediting organizations, require one or two
beds to be kept, designated, and equipped in a
hospital or nursing home as isolation beds.
Host-Related Control and Prevention
 Quarantine applies to persons who have been
exposed to a contagious disease but may or may
not become ill
What Is Malnutrition?
 A condition that arises when the body does not get
the right amount of vitamins, minerals, and other
nutrients to maintain healthy tissues and proper
organ function. Malnutrition occurs in people
experiencing either undernutrition or overnutrition.
What are some common nutritional
deficiency diseases and disorders?
 Kwashiorkor – protein deficiency
 Marasmus – protein-calorie malnutrition, chronic
undernutrition
 Iron-deficiency anemia
 Folic acid-deficiency anemia
 Vitamin B12-deficiency anemia
 Xerophthalmia – vitamin A deficiency
 Endemic goiter – iodine deficiency
 Beriberi – thiamine deficiency
What are some common nutritional
deficiency diseases and disorders?
 Ariboflavinosis – riboflavin deficiency
 Pellagra – niacin and amino acid tryptophan
deficiency
 Scurvy – vitamin C deficiency
 Rickets – vitamin D deficiency
 Tetany – mineral deficiency
 Osteomalacia and osteoporosis – impaired calcium
and phosphorus metabolism affecting bone
formation
Undernutrition
 A consequence of consuming too little essential
vitamins, minerals, and other nutrients, or excreting
them faster than they can be replenished
 Inadequate intake may result from excessive
dieting, severe injury, or serious illness
 Excessive loss may result from diarrhea, heavy
sweating, heavy bleeding, or kidney failure
Overnutrition
 The consumption of too much food, eating too
many of the wrong things, too little physical
activity and exercise, or taking too many
vitamins or dietary supplements
Selected Chronic Diseases and
Conditions
 Cardiovascular disease, cancer, chronic obstructive
pulmonary disease, diabetes mellitus, and mental
health disorders
 Chronic diseases are not typically caused by an
infectious agent (pathogen), but result of genetic
susceptibility, lifestyle, or environmental exposures
 Some exceptions are cancers of the cervix, liver,
and stomach
Characteristics of Chronic Diseases
 The latency period for chronic diseases is typically
more difficult to identify than is the incubation
period for acute infectious diseases
 This is explained by the multifactorial etiology that
characterizes many chronic diseases
Disability
 Umbrella term for impairments, activity limitations,
and participation restrictions
 Impairments – any loss or abnormality of psychological,
physiologic, or anatomic structure or function
 Activity limitations – difficulties an individual may have
in executing activities
 Participation restrictions – problems an individual may
experience in involvement in life situations