Module 4: Epidemiology History and Concepts

• Module 4 Topics

Historical Roots

• Hippocrates explained diseases from a rational, not supernatural, perspective.
• Edward Jenner, the "father of immunology", created the smallpox vaccination.
• John Snow, the "father of epidemiology", investigated a cholera outbreak in London, characterizing its start, peak, and decline.
• Florence Nightingale contributed to the Crimean war.
• William Farr created the first national vital statistics system and collaborated with Florence Nightingale in British Army studies.
• Sanitary statistics link sanitary conditions to disease.
• Infectious disease epidemiology focuses on microorganisms as a cause of disease.
• Chronic disease epidemiology concerns non-infectious diseases as a cause of health problems.
• Eco-epidemiology examines resistant organisms, genetics, and technology

Epidemiology Concepts

• Epidemics refer to instances where disease occurrence exceeds the expected norm.
• Pandemics involve worldwide distribution of diseases.
• Endemic diseases are those most frequently found in specific areas.
• The epidemiologic triangle consists of host, agent, and environment.
• Host refers to a susceptible human or animal housing a disease-causing agent.
• Agent refers to a factor causing or contributing to a health problem (biological, chemical, nutrient, physical, or psychological).
• Environment includes all external factors that might influence vulnerability or resistance (physical or psychosocial).
• Disease causality is evaluated using 9 criteria to relate environmental exposure and health outcomes.

Disease Causality Criteria

• Strength of association reflects the ratio of disease rate in those with a suspected causal factor versus those without, with a higher rate indicating a strong association.
• Consistency of association means the association is observed across various studies in different groups and can be replicated.
• Specificity suggests a cause leads to one effect, which isn't always the case in noninfectious diseases.
• Temporality requires that exposure to the suspected factor must precede the onset of the disease.
• Biological gradient means that increasing exposure to the disease-causing factor corresponds to an increased disease occurrence.
• Biological plausibility means the hypothesized cause aligns with current scientific models.
• Coherence of explanation means the hypothesized cause aligns with scientific knowledge.
• Analogy refers to similarities between the association of interest and others.
• Experimental evidence means experimental and non-experimental studies support the association.
• Causality defines the relationship between a cause and its effect.

Chain of Causation

• Reservoir indicates where the agent lives and multiplies.
• Portal of exit refers to how the agent leaves the reservoir and enters a new host.
• Mode of transmission describes how the agent gets into its new host.
• Agent is what causes the disease.
• Portal of entry is where the agent enters the new host.
• Host is the new carrier of the organism.

Types of Immunity

• Active immunity is produced by the person's own immune system.
• Passive immunity is protection transferred from another animal or human.
• Cross immunity means immunity to one bacteria or virus is effective in protecting against an antigenically similar but different organism.
• Herd immunity is the immunity level present within a population group.
• Risk is the probability that a disease or other unfavorable health condition will develop.
• Natural history refers to the progression of events that occur before the development of a disease, during its course, and its conclusion.
• It has four stages:
  • Susceptibility, where the disease is not present and the individual hasn't been exposed.
  • Subclinical, where the individual has been exposed but is asymptomatic.
  • Clinical, where signs or symptoms develop and diagnosis may occur.
  • Resolution or advanced disease, which can lead to a return to health, a chronic form of the disease, or death.

Causal Relationships

• Cross-sectional studies explores health conditions relation to other variables in a specified population at a specific point in time, can show that the factor and the problem coexist
• Retrospective studies look backward to find causal relationships, often using existing data.
• Prospective studies look forward to find causal relationships, ensuring the presumed causal factor precedes the health problem.
• Experimental studies control or change suspected factors and observe results to confirm associations.
• Causal relationships exist if the factor of interest increases the probability of disease occurrence in different populations, and evidence suggests decreasing the factor reduces disease frequency.

Sources of Information

• Vital statistics include data from registrations of births, deaths, adoptions, divorces, and marriages and are the most useful in epidemiologic studies.
• Census data includes age, sex, race, ethnic background, occupation, income, marital status, education, and housing quality.
• Reportable diseases must be reported at both state and national levels.
• Disease registries are rosters for conditions with major public health impact.
  • Includes:
    • National Amyotrophic Lateral Sclerosis Registry
    • Rapid Response Registry
    • World Trade Center Health Registry.
• The CDC maintains surveillance systems to monitor diseases for control strategies.
• State governments monitor environmental hazards through health departments.
• The National Center for Health Statistics Health Surveys provides health prevalence data.
• The CDC issues the Mortality and Morbidity Weekly Report for summaries of disease and death data trends.
• Informal observational studies involve informal observation and description.
• Scientific studies are also used as sources of information.

Epidemiological Investigative Process

• Descriptive epidemiology investigates patterns of health conditions in a population.
• Counts reflect the number of people.
• Rates reflect the proportion of people.
• Analytic epidemiology examines patterns of occurrence.
  • Includes:
    • Prevalence studies
    • Case-control studies
    • Cohort studies
• Incidence is all new cases of a condition appearing during a given time, helps track the progression of a disease using the calculation: (number of new cases)/(persons at risk)
• Prevalence is important for tracking chronic disease using the calculation: (number of people with condition)/(total number of population)
• Case specific mortality rate uses the calculation: (number of deaths from condition)/(total number of persons with condition)*100 (percent)
• Cause specific mortality rate uses the calculation: (number of deaths from a cause/condition)/(estimated total population)

Module 5 Concepts

• Communicable diseases are caused by infectious agents (virus or bacteria) that can be transmitted.
• Challenges in communicable disease include human migration, travel, globalization, diseases with epidemic potential, climate variability, antibiotic-resistant strains, and bioterrorism.
• Community health nurse's role in communicable disease in supporting the state health department.
• Disease reporting laws are derived from state, federal, and global regulations.
• Any outbreak or unusually high incidence of disease must be reported.
• The CDC provides support to local or state health departments.
• The local health department is the initial point of notification for communicable diseases.

Modes of Transmission of Infection

• Direct transmission from reservoir to host includes direct contact or droplet spread.
• Examples such as contact or droplet
• Indirect transmission from reservoir to host includes suspended air particles, inanimate objects (vehicles), or animate intermediaries (vectors).
• Examples such as airborne/formites.
• Vectors are animate intermediaries such as insects.
• Food and water-related contamination can occur at the source, through unsanitary handling, or due to improper storage.
• Investigating food/water outbreaks involves epidemiologic data, traceback data, and food/environmental testing data.

Tuberculosis

• 1/3 of the world population has latent TB.
• It is one of the ten leading causes of death globally.
• 3 Categories:
• TB
• Multidrug resistant
• TB with HIV (the leading killer of HIV positive people)
• 2 Stages:
• Latent
• Active
• Screening via Mantoux TST, or Blood test
• Test those if who spent time with someone with TB, from a country where TB is common, live or work in high-risk settings, healthcare workers who care for patients with high risk, infants, children, adolescents exposed to adults who are at increased risk
• Prevent using Primary, Secondary, or Tertiary approaches

Chlamydia

• This is the most commonly reported notifiable STD.
• Complications include ectopic pregnancy, pelvic inflammatory disease, infertility, premature delivery, and low birth weight.
• Most new cases are in 20-24 year olds, and most people have no symptoms.
• Screening guidelines suggest yearly tests for sexually active women 24 or younger, those over 24 with multiple partners, and pregnant women. Testing considered for men who have sex with men in high rate settings.
• Treatment includes antibiotics, such as 7 days or 1 dose (followed by 7 days of abstinence).

Bioterrorism

• This is the deliberate release of biological agents into society with the intent to cause harm.
  • Anthrax is found in soil or animal skins and is a bacterial disease.
    • Person-to-person transmission is rare.
    • Spores may live on soil or articles for decades.
    • Incubation: 5-7 days
    • 85-90% death rate for inhaled anthrax
  • Smallpox only exists in 2 places.
    • Person-to-person
    • Respiratory droplets or skin
    • Vaccination
    • Considered eradicated since 1980

Primary Prevention

• Education must reach the target population and consider cultural context.
• Immunizations are beneficial and have a high return on investment.
• Advisory Committee on Immunization Practices makes recommendations on immunization practices
• Challenges include opposition to government mandates, inconsistent exempt criteria, and negative information.
• National Immunization Survey shows >80% of children are vaccinated, while adult immunization rates are low.
• Combat vaccine hesitancy by corroborating concerns, building trust, providing scientific explanations, and explaining information.
• Low vaccination levels among adults are due to lack of medical care, reminder systems, provider knowledge, patient awareness, misinformation, and cost.

Adult Vaccinations

• Shingles
• Hepatitis B
• Pneumococcal Boosters:
• Tetanus-10 years
• Pertussis- 10 years
• Influenza-yearly
• Pneumococcal- 1 or 5 years depending
• Secondary prevention involves screening to identify persons for further evaluation and treatment.
• Tertiary prevention includes care, treatment, isolation, and safe handling of infectious wastes.
• The P/CHN's job is to balance public health interventions and individual rights while protecting the health and safety of the community.

Enforced Compliance

• Enforcing compliance or restricting activity of infected people protects the welfare of others.
• Confidentiality protects the privacy of the individual by disclosing only necessary information.
• Social and community COEs are protected from discrimination but not with respect to posing a public health threat.

Module 6 Concepts

• Ecosystems include living and non-living things, with organisms connected and dependent on each other.
• Sustainability means human beings and the natural environment must coexist harmoniously.
• Upstream Focus to address root causes that influence health at the institutional and system level rather than focusing on healthy lifestyle issues

Health Disparities

• Preventable factors and differences disproportionately affecting certain groups
  • Includes: socioeconomic status/income, race/ethnicity, age, sex/gender, geography, disability, sexual orientation, immigrant status, religion, and mental health status.
• Social determinants of health are conditions in which people are born, grow, live, work, and age.
• Five determinants:
  • Economic stability
  • Education access and quality
  • Health care access and quality
  • Neighborhood context
• Environmental justice ensures fair treatment and involvement of all people regardless of race, color, origin, or income.
• The precautionary principle means that precautionary measures should be taken when an activity raises threats of harm, even if cause-and-effect relationships are not fully established.
• Health risk assessment involves relying on existing science to assess and determine environmental risks.

Specific Vulnerabilities

• Exposures for pregnant women create risks to both the mother and fetus.
  • Examples: fetal loss, low birth weight, menstrual abnormalities, reduced fertility, and neurodevelopmental performance.
• In infants and children, effects include ADHD, antisocial behaviors, and autism.
• Individual assessment should complete a personal environmental health exposure assessment
• Includes:
• I: investigate potential exposures
• P: present work
• R: residence
• E: environmental concerns
• P: past work
• A: activities
• R: referrals and resources
• E: educate
• Home assessment includes identifying common hazards such as asbestos, arsenic, carbon monoxide, formaldehyde, lead, mold, pests, pesticides, radon, and volatile organic compounds.
• Community assessment involves windshield or walking surveys to assess the physical environment, health and safety, community resources, transportation, and social interaction.
• Built environment includes all aspects of the environment that are not naturally occurring and contribute to social disruption and impacts indoor and outdoor physical environments where people live, work, and engage.

Types of Toxic Exposure

• Air pollution includes aerosols, air pollutants, VOCs, hydrofluorocarbons, and gases.
• Water
• Foodborne illnesses affects at least 3000 people a year.
• C/HPNs include environmental health in their practice and their roles through assessment, policy development, and assurance.
• Disasters are often characterized by cause, such as natural disasters (earthquakes and tsunamis) or man-made disasters (mass shootings).
• A casualty is someone injured or killed as a direct result of an accident or natural disaster.
• Multiple casualty incident involves more than 2 people but fewer than 100.

Disaster Scope

• This is the range of the effect either geographically or in terms of the number of people affected.
• Intensity of a disaster is the level of destruction and devastation it causes.
• Factors contributing to disasters include host, agent, and environment.
• Host include age, general health, mobility, psychological factors, and socioeconomic factors
• Agent is the natural or technologic element that causes the disaster.
• Environment is those that could potentially contribute to or mitigate a disaster.
• Phases of disaster management include prevention/mitigation, preparedness, response, and recovery.
• Prevention/mitigation prevents future emergencies and minimize the effects.
• Preparedness improves community and individual responses.
• Response begins immediately after the onset of the disaster and emergency.
• Recovery takes place after an emergency and restore health and social/economic vitality to the community.

Prevention Strategies

• Primary prevention keeps the disaster from happening by minimizing damage through training, identifying high-risk groups, and working with community partners.
• Secondary prevention focuses on earliest possible detection and treatment.
• Tertiary prevention reduces the degree of disability or damage.
• Primary prevention can be most effective when the C/PHN has done a complete community assessment, collaborates with community leaders to provide education and promote policies, provides anticipatory guidance, and has an active role in the community
• Preparing for disasters includes personal preparedness, assessment, establishing authority community and transportation, mobilizing warning and evacuating
• Disasters include Rescue & Triage

Triage Strategies

• Simple
• Triage
• And
• Rapid
• Treatment
• Triage should take place within 30-60 seconds
• Examples include black tag-deceased, red tag-immediate, yellow tag- delayed, and green tag-walking wounded/minor
• Recovering from disasters is also a key thing to keep in mind
• Primary prevention in disasters is building competency or resilience through behavioral health promotion.
• Secondary prevention is debriefing and crisis intervention.
• Tertiary prevention is recognition and treatment for acute stress disorder or PTSD.

Terrorism

• Bioterrorism is categorized with A, B, or C. The outcome is fear, death, and destruction.
• Category A agents pose the highest risk and includes emerging pathogens for mass dissemination.
• Chemical warfare includes explosives, nerve agents, blister agents, and riot control agents.
• Preparedness in disasters include:
  • Parents/guardians awareness of their children's school emergency and evacuation plans
  • Actions to take should a contagious disease occur
  • Adults who are aware of the transportation needs should a disaster occur and they need to evacuate Household emergency plan that includes vulnerable individuals