Introduction to Epidemiology Flashcards
Epidemiology
Study of factors that determine the occurrence and distribution of disease in a population
Epidemiologists
Public health professionals who investigate patterns, causes of disease, and injury in humans
Classical epidemiology
• Population oriented
• Studies the community origins of health problems
• Interested in discovering risk factors
Clinical epidemiology
• Studies patients in health care settings
• Improve prevention, early detection, diagnosis, treatment, prognosis, and care of illness in individuals
Syndromic epidemiology
• Looks for patterns of signs and symptoms
that indicate an origin in bioterrorism
Infectious disease epidemiology
• Study of the complex relationships among
hosts and infectious agents
Chronic disease epidemiology
• Addresses the etiology, prevention, distribution, natural history, and treatment outcomes of chronic health disorders
Public Health
science and art of preventing diseases
LEVELS OF SCIENTIFIC STUDY OF DISEASE
- Submolecular or molecular level (e.g. cell biology, genetics, biochemistry, and immunology)
- Tissue or organ level (e.g.anatomic pathology)
- Level of individual patients (e.g. clinical medicine)
- Level of populations (e.g.epidemiology)
Pre-disease
Primary prevention;
• Health promotion
• Specific protection
Latent disease
Secondary prevention;
• Pre-symptomatic
• Diagnosis and Treatment
Symptomatic disease
Tertiary prevention;
• Disability limitation for early symptomatic disease
• Rehabilitation for late symptomatic disease
HOST FACTORS
Responsible for the degree to which the individual is able to adapt to the stressors produced by the agent
HOST RESISTANCE
• Genotype
• Nutritional status
• Body mass index
• Immune system
• Social behavior
AGENTS OF DISEASE OR ILLNESS
• Biologic agents
• Chemical agents
• Physical agents
• Social and psychological stressors
BIOLOGIC AGENTS
• Allergens, infectious organisms, biological toxins, foods
CHEMICAL AGENTS
• Chemical toxins, dusts
PHYSICAL AGENTS
• Kinetic energy, radiation, heat, cold, noise
SOCIAL AND PSYCHOLOGICAL FACTORS
• Anxiety, depression
ENVIRONMENT
Influences the probability and circumstances of contact between the host and the agent
To be an effective transmitter of disease,
a vector must have a specific relationship to the agent, the environment, and the host
VECTORS
• Insects, arachnids, mammals
• Human groups
• Inanimate objects
• Part of the environment
RISK FACTORS AND PREVENTABLE CAUSES
• Intrinsic factors
• Extrinsic factors
INTRINSIC FACTORS
genetics, nutritional status, reproductive activities, personal behavior
EXTRINSIC FACTORS
man-made or naturally occurring carcinogens, viral infections, etc.
BIOLOGIC AND BEHAVIORAL FACTORS
Influenced by gender, age, weight, bone density, etc.
Risk factors for Biological and Behavioral Factors
- Cigarette smoking
• Overweight / obesity
• Unprotected sexual intercourse
• Excessive alcohol intake
• Abuse of legal and illegal drugs
• Driving under the influence
• Homicide / suicide attempts
ENVIRONMENTAL FACTORS
Epidemiologists describe the patterns of the disease, develop and test hypotheses about causal factors, and introduce methods to prevent further cases of disease
SMALLPOX
• First infectious disease known to
have been eradicated from the globe
HERD IMMUNITY
When a vaccine diminishes an immunized person’s ability to spread the disease, leading to reduced disease transmission
IMMUNODEFICIENCY
• Genetic abnormalities
• Infections, certain medications
NUTRITIONAL FACTORS
Dietary variations play an important role in producing differences in disease rates among populations
• Genetic epidemiology
• Addresses the distribution of normal and abnormal genes in a given population
• Heritability
• Contribution of genes relative to
all determinants of disease
• Genetic screening
• Important in identifying problems in newborns and in determining susceptibility genes
• Medical care services
• May be beneficial to health but
can also be dangerous
Iatrogenic disease
Occurs when a disease is induced inadvertently by treatment or during a diagnostic procedure
Personal beliefs, religious faith, family support, social networks
Social and spiritual factors
- VACCINATION AND PATTERNS OF IMMUNITY
Degree of immunity necessary to eliminate a disease from a population varies depending on the type of infectious organism, the time of year, and the density and social patterns of the population
DIPHTHERIA
Corynebacterium diphtheriae;
• Vaccine-produced immunity decreases over time
• Recommendation: additional single vaccination for adults to provide natural booster effect
SMALLPOX
Variola virus;
• Variola minor (ALASTRIM)
• Variola major (Classical smallpox)
EDWARD JENNER
used cowpox virus to create a vaccine for smallpox
POLIOMYELITIS
Causative agent = Poliovirus; fecal-oral route or by vehicle (food)
TYPES OF VACCINES FOR POLIO
• Inactivated or killed polio vaccine (IPV) / Salk
• Live, attenuated oral polio vaccine (OPV) / Sabin
SYPHILIS
caused by the spirochete bacteria: Treponema pallidum subspecies pallidum
Three Stages of Syphilis
Primary, Secondary, Tertiary
PRIMARY STAGE OF SYPHILIS
3-90 days after exposure, appearance of painless sore/ ulcer called CHANCRE
SECONDARY STAGE OF SYPHILIS
4-10 weeks after initial infection; rough and reddish brown rashes, flu-like symptoms, warts
TERTIARY STAGE OF SYPHILIS
3-15 years after initial infection; no symptoms but bacteria is still present
19th century:
• Diarrhea – primary killer of children
• Tuberculosis – leading cause of adult mortality
Sanitary revolution:
• Reduced infant mortality, increased
effective birth rate but a cause of today’s worldwide
population problem
Demographic gap
• Difference between birth rate and death rate that develops when a country undergoes demographic transition
Synergism
• Interaction or combination of factors that produce a greater effect than the sum of their separate effects
Malnutrition and Infection
• A malnourished child has more difficulty making antibodies and repairing tissue damage which makes the child less resistant to infectious diseases
Antigenic shift
• a process by which 2 or more strains of a virus combine to form a new subtype of a virus
Antigenic drift
• Accumulation of mutations within virus genes over time
Global pandemic
Widespread outbreak involving multiple continents
Biologic spectrum of disease (Iceberg phenomenon)
• Variation in the severity of a disease process
• Paramount to the field of epidemiology
Field trials
• Randomized trials of preventive measures
• Important phase of evaluating a new vaccine
Ongoing/continued surveillance programs
• Ensure a vaccine’s continued safety and effectiveness
• Examples: polio, smallpox, measles
Current recommendation for measles vaccine:
initially at 15 months of age, booster dose at 4 to 6 years of age
Syndromic surveillance
Epidemiologists contributing to national security
SETTING DISEASE CONTROL PRIORITIES
“Disease control priorities should be based not only on the currently existing size of the population (and its problem), but also on the potential of a disease to spread to others; its likelihood of causing death and disability; and its cost to individuals, families, and the community.”
EXAMPLES OF DISEASE CONTROL PRIORITIES
Examples:
• HIV/AIDS prioritization
• Type 2 diabetes
• Severe Acute Respiratory Syndrome (SARS)
• Zoonotic infections like avian influenza (H5N1)
Diagnosis
Process of identifying the nature and cause of a disease through evaluation of the clinical history, review of symptoms, examination or testing
Effective treatment
Determined by methods of clinical epidemiology
Prognosis
• Improved understanding through epidemiology
Risk estimation
Epidemiology forecasts the probability and impact of risks
Epidemiologists can be called to testify in court:
• Product hazards
• Probable risks and effects of various environmental exposures and medications
Lawsuits may rely on epidemiologic data:
• General environmental exposures
• Occupational illness claims
• Medical liability
• Product liability
