epidemiology: pop health 336

Epidemiology

population medicine

Study of the distribution/ determinants of health/ disease in human populations.

who is the father of epidemiology

john snow from with works with cholera

how is epidemiology used

¡To monitor and improve the health of the population and communities.

¡Investigate and evaluate interventions to prevent disease and maintain health.

¡Data can be used to prevent disease outbreaks or determine effectiveness of prevention effort.

how old is epidemiology

dates back to Hippocrates, 300 BC

who is the first nurse epidemiologist

florence nightingale, focused on sanitation and preventative disease thru the work she collected from dead soldiers in the crimean war

what is the historical focus of epidemiology

•Acute illnesses (< 3 months)

•Epidemics (e.g., John Snow, cholera)

what is the current focus of epidemiology

•Chronic diseases

•Pandemics

•Other health-related events

what is an epidemic

•unexpectedly large number of cases of an illness, specific health-related behavior, or event in a particular population (HIV)

what is an endemic

•disease that occurs regularly in a population as a matter of course (Heart Disease/Malaria)

what is an endemic

•disease that occurs regularly in a population as a matter of course (Heart Disease/Malaria)

what is a pandemic

•outbreak over wide geographic area (COVID-19/1918 influeza)

what is epidemiology

•study of distribution and determinants of health-related states or events in specified populations

why study epidemiology?

•Burden of disease in populations

•Make meaningful comparison of disease frequency between

what are the 5 major factors of epidemiology

•Describes the occurrence of a disease or health disorder

•Distribution—”Who” has the disease, where, when

•Frequency—”How often” were they affected

•Population

•Determinants

Analytic Epidemiology

Identifies when and where prevention is possible thru looking at the host, agent and environment

what is the host and what are host factors:

•Susceptible person or population

Influence Exposure, Susceptibility, or Response to Agent

what are factors affecting the host

•Age & gender

•Genetic susceptibility

•Immunologic status

•Lifestyle factors:  diet, exercise, etc.

agent

factor(s) that causes or contributes to a health problem à causative factor

what are some infectious agents

•bacteria, fungi, viruses, parasites

what are chemical agents

•pesticides, toxic chemicals (industrial waste, paint)

what are physical agents

“““ exposure to physical elements (radiation)

what is the environment in factors

•External factors that influence agent and host vulnerability

Communicable (Infectious)

¡diseases for which biological agents or their products are the cause and that are transmissible from one individual to another

Non-communicable (Noninfectious)–

illnesses that cannot be transmitted from one person to another

Multi-causation disease model

Host:  inalterable, unique genetic endowment

Personality, beliefs, behavioral choices:  impact host

Complex environment:  exposes host to risk factors

acute disease

less than 3 months

chronic disease

more than 3 months

Web of Causation

Causes of disease interact and are interrelated

Direct Transmission

¡Immediate transfer of disease agent between infected and susceptible individuals

¡Touching, biting, kissing, sexual intercourse

Indirect Transmission

¡Transmission involving an intermediate step

¡Vehicle-borne (inanimate object) 

¡Vector-borne (animals or insects) 

diseases that are direct transmission

¡STIs

¡Mono

¡Impetigo 

¡Lice Scabies

diseases that are airborne

¡Measles

¡Chickenpox

¡TB

¡Influenza

food bornediseases

norovirus

salmonellosis

Hep A

E. coli

Food intoxication: Dlostridium botulinum

Active surveillance

purposefully seeking out new cases of disease

Passive survellance

more commonly used by local/state health dept

Notifiable diseases

infectious diseases in which health officials request or require reporting; can become epidemics

¡Reported to CDC via National Electronic Telecommunications System (NETS)

•Routinely collected data

•Vital records (birth and death certificates)

•Surveillance data from the Centers for Disease Control and Prevention (CDC

•Original data:

•specific for epidemiological studies

Monthly Vital Statistics Report

¡Vital statistics are summaries of records of major life events: birth, death, marriage, divorce

¡Published by National Center for Health Statistics under the CDC

¡Also calculates death rates by race and age

Morbidity & Mortality Weekly Report (MMWR)

¡Prepared by CDC from state health department reports

¡Reports morbidity & mortality data by state and region of U.S.

¡Example: Youth Risk Behavior Surveillance

•Risk

•Probability that an event will occur within a specified time period; considers risk factors

•Rate

•measure of the frequency of a health event in a defined population in a specified period; morbidity/mortality/natality

•Attack rate

•Proportion of persons who are exposed to an agent and develop the disease; is often specific to an exposure. Is a %

•Secondary attack rate refers to the spread of disease in a family, household, dwelling unit, dormitory, or similar circumscribed group.

•Incidence rate

•Occurrence of new cases of a disease over a period

•Important in study of acute diseases – diseases in which the peak severity of symptoms occurs and subsides within days or weeks

•Mortality statistics:

•most reliable measure of population health status

•Life expectancy:

•average number of years a person from a specific cohort is projected to live from a given point in time

•Crude rates: 

•a rate in which the denominator includes the total population

•Age-adjusted rates: 

•used to make comparisons of relative risks across groups and over time when groups differ in age structure

•Ratios

•compares one number with another/ compare one at-risk population to another

•Prevalence

•measures all existing cases at a given time (includes incidence [new cases] and all existing cases; useful measuring chronic illness in population and for planning for health care services, resources and facilities, determining health care personnel needs and evaluating treatments that prolong life

Experimental Study

Treatments and exposures occur in a controlled setting (i.e., randomized control trial)

Cross-Sectional Study

Examines or surveys exposures and outcomes (e.g., disease present or not) at one point in time.

Prospective Time Frame of Studies

Looks forward in time, examines future events, follows a disease or condition or group of people over time

Retrospective Time Frame of Studies

Looks back in time, examines events that have already occurred

Community-oriented epidemiology

¡Involves observation, data collection, consultation, and interpretation

Data can be presented as percentages (%), ratios (1:1), rates (# of events)

¡Assessment of health needs

Example: when determining what interventions are needed, community health nurse can compare current rate of disease to previous rate of disease

¡Understanding factors that influence health and disease

¡ Attributable risk ex: Lung cancer--- smoking

¡Subtract the rate of disease among non-exposed individuals from the rate of disease among those exposed.

Prevention-

Planning & taking action to prevent the onset of disease or a health problem

Control-

Efforts to control / contain a disease

Elimination-

¡Stopping a disease in a defined geographical region (e.g., polio, guinea worm)

Eradication-

Total elimination from the world population

•Primary prevention

• Prevent disease/injury, stop sthe disease before it starts

•Secondary prevention

•early diagnosis and prompt treatment before disease becomes advanced and disability severe

•Tertiary prevention

•Aimed at rehabilitation following significant pathogenesis; retrain, reeducate, rehabilitate

primary prevention for communicable diseases in individuals

¡Hand washing, using condoms, properly cooking food

primary prevention for communicable diseases in communities

¡Chlorinating water supply, inspecting restaurants, immunization programs for all citizens, vector control, solid waste disposal

primary prevention for non-communicable diseases in individuals

Education and knowledge about health and disease prevention, eating properly, adequate exercise, driving safely

primary prevention for non-communicable diseases in communities

¡Adequate food and energy supplies, efficient community services, opportunities for education, employment, and housing

Secondary Prevention of Diseases for communicable disease in individuas

¡Self-diagnosis, self-treatment w/home remedies

Secondary Prevention of Diseases for communicable disease in communities

¡Controlling or limiting extent of an epidemic

¡Carefully maintaining records; investigating cases

Secondary Prevention of Diseases for noncommunicable disease in communities

Provision of mass screenings for chronic diseases, case-finding measures, provision of adequate health personnel, equipment and facilities

Secondary Prevention of Diseases for noncommunicable disease in individuals

Personal screenings (mammography, PSA test), regular medical & dental exams, pursuit of diagnosis and prompt treatment

Tertiary Prevention of Diseases for communicable diseases in individuals

Recovery to full health after infection; return to normal activity

Tertiary Prevention of Diseases for communicable diseases in communities

¡Preventing recurrence of epidemics

¡Removal, embalming, burial of dead

¡Reapplication of primary & secondary measures

Tertiary Prevention of Diseases for non-communicable diseases in communities

Adequate emergency medical personnel and services:  hospitals, surgeons, nurses, ambulance services. 

Tertiary Prevention of Diseases for non-communicable diseases in individuals

Significant behavioral or lifestyle changes, adherence to prescribed medications, following rehabilitation requirements after surgery

Natural Acquired immunity

–Active:     Exposed to antigen

–Passive:   Contains antibodies

               (colostrum in breast milk, placenta)

Artificial Acquired immunity

–Active:   Vaccine of live or tamed virus/portion of virus

–Passive:  Antibody injection (gamma globulin, plasma proteins, antitoxins)

what is herd immunity

if most people get vaccinated, the spreading of the virus is contained