Epidemiology and Communicable Diseases Study Notes

Epidemiology and Communicable Diseases

  • Epidemiology is the study of disease.
  • Nurses assist epidemiologists through surveillance, which is monitoring disease trends.
  • Chapter 7 in Lippincott provides an in-depth discussion of epidemiology.
  • Florence Nightingale was one of the first healthcare workers to use epidemiology, using calculations and trends to develop her theory of the environment.
  • Surveillance involves watching the rates of diseases to identify increases or decreases.
  • It also involves looking to see where the disease is occurring the most (regionally or globally).
  • Epidemiology is used to understand modes of transmission, incubation periods, early manifestations, and periods of communicability.
  • It helps determine how to intervene and why some people are more affected than others.
  • Nurses use epidemiology to:
    • Understand disease patterns and trends.
    • Provide risk assessment.
    • Develop protocols to prevent and control the spread of infections.
    • Understand the impact of disease and death on populations.
    • Effectively take measures to prevent disease (vaccinations, education).
    • Use targeted programs for interventions.
    • Advocate for policies and resources.
    • Identify cases and recognize patterns.
    • Evaluate the effectiveness of nursing interventions in acute care settings.

Epidemiological Triangle

The epidemiological triangle consists of the host, environment, and agent. (Lippincott pages 157-159)

  • Host: The person susceptible to the disease or health problem.
    • Factors influencing risk:
      • Physical factors: Age, sex, race.
      • Socioeconomic status, genetic influences.
      • Immunological and physiological status.
      • Occupation.
      • Psychological factors: Response to stress.
      • Lifestyle factors: Diet, exercise, healthy and unhealthy practices (smoking, high-fat foods).
      • These factors can affect the immune system and resistance to pathogens.
  • Environment: Outside factors surrounding the host that influence vulnerability.
    • Physical environment: Climate, geography, weather patterns, safety of buildings, water and food supply.
      • Pictures Dr. Boots showed the people's environments where it might be really polluted.
    • Presence of animals: Domestic or wild animals (vectors and reservoirs).
    • Plants, insects, or microorganisms: Reservoirs (harbor microorganisms) and vectors (carry disease).
    • Vectors are those insects or those animals that carry a disease and reservoirs harbor and nourish microorganisms.
    • Social and psychosocial environment: Social, cultural, economic, and psychological influences and conditions.
      • Access to healthcare, quality of healthcare, cultural health practices.
      • Poverty, working conditions, work stressors, life stressors: psychological or psychosocial factors that affect a person's health as well as their immunological response.
  • Agent: The factor that causes or contributes to the disease or health condition.
    • Infectious agents: Viruses, bacteria, fungus, parasites cause infectious diseases.
    • Can be present in a person's bloodstream or on a rocks in a mountain road.
    • Chemical agents: Drugs, toxins, lack of chemicals (vitamin deficiency), lack of seatbelts.
      • Opioids.
    • Physical agents: Noise and temperature (can also be linked to environment).
      • Noise: Can cause hearing loss, difficulty concentrating, communication problems, workplace accidents, and stress from noisy environments (jet engines, jackhammers).
      • Temperature: High temperatures can cause heat stroke and dehydration in people who are working outside; cold temperatures can cause frostbite and increase the chance of death for homeless people.

Epidemiological Calculations

  • Incidence: New cases during a certain time period.
  • Prevalence: Existing cases.
  • Attack Rate: Describes new cases, especially in new or self-contained diseases.

Prevalence Calculation

  • Formula: Number of existing cases at a specific timeTotal Population×Multiplier\frac{\text{Number of existing cases at a specific time}}{\text{Total Population}} \times \text{Multiplier}
  • Example: County nurse calculates COVID prevalence between January and February.
    • Total population: 1232.
    • COVID cases during this period: 12.
    • Calculation: 121232=0.0097\frac{12}{1232} = 0.0097
    • Multiply by 1000: 0.0097×1000=9.740.0097 \times 1000 = 9.74 per 1000 people.

Incidence Calculation

  • Formula: Number of new cases during a specific timeTotal Population×Multiplier\frac{\text{Number of new cases during a specific time}}{\text{Total Population}} \times \text{Multiplier}
  • Example: Calculate incidence rate for February, given 3 new cases in February.
    • Calculation: 31232=0.0024\frac{3}{1232} = 0.0024
    • Multiply by 1000: 0.0024×1000=2.40.0024 \times 1000 = 2.4 per 1000 people.
  • Important points:
    • Context matters when analyzing disease statistics.
    • Small towns can have high incidence rates due to the high percentage of the population affected.
    • Statistics for health outcomes may be skewed due to specialized hospitals receiving high-risk patients.

Disease Terminology

  • Endemic: Disease present in the population all the time.
    • E.g., influenza in the US, malaria in tropical countries.
  • Epidemic: Disease occurring in a broader area and becoming larger.
  • Pandemic: Affects more than one country, usually multiple countries or continents.
    • Declared by the World Health Organization (WHO).
    • E.g., COVID, AIDS.

Communicable Diseases

  • Lower respiratory tract infections caused the most deaths in 2020 worldwide.
  • Deaths due to diarrheal diseases and tuberculosis have declined, but are still concerning.
  • Communicable disease: Can be transmitted from one host to another.
    • Caused by an infectious agent and transmitted from a source or reservoir to a susceptible host.
  • Diseases of most concern:
    • Pertussis, HIV/AIDS, hepatitis, influenza, COVID-19, pneumonia, tuberculosis, gonorrhea, drug-resistant organisms (MRSA).
  • Virulence: How ill a disease makes a person.
  • Carriers: People who carry a disease without symptoms but can still spread it.
  • Leading causes of communicable disease deaths:
    • Acute lower respiratory tract infections (pneumonia, influenza), HIV/AIDS, diarrheal diseases (cholera, typhus), tuberculosis, malaria, viral hepatitis, and sexually transmitted infections.
  • Routine immunizations are recommended by the CDC.
    • Public health nurses administer and track immunizations, provide education, and address barriers to immunizations.
    • Vaccine hesitancy should be addressed with informed information to allow individuals to make informed decisions.
    • Vaccines are licensed, and the US FDA requires testing to ensure safety before administration.
    • Vaccine failure occurs if the immune system does not produce enough antibodies (primary vaccine failure) or antibody levels fall over time (secondary vaccine failure).

Populations at risk for communicable diseases:

  • Young children.
  • Older adults.
  • Immunosuppressed people.
  • Clients with a high-risk lifestyle.
  • International travelers.
  • Healthcare workers.

Disease Transmission

  • Vertical Transmission: From mother to child.
    • Examples: Zika virus, sexually transmitted infections.
    • Prenatal infections.
  • Horizontal Transmission: From one person to another.
    • Airborne: Respiratory diseases through droplets or particles.
      • Droplets: Heavy and dense, fall within three feet (pertussis, influenza, SARS, colds).
      • Particles: Lighter, travel further than three feet (measles, chickenpox, tuberculosis, COVID).
    • Foodborne:
      • Food Infection: Caused by bacteria or viruses (norovirus, salmonella, shigella, hepatitis A, E. coli, listeria).
      • Food Intoxication: Caused by toxins produced by bacteria or viruses (staphylococcus aureus, clostridium botulinum).
        • Botulism: Due to Clostridium botulinum in raw honey or improperly sterilized canned food; can be severe and fatal in infants.
    • Waterborne: Caused by fecal contamination of water (cholera, typhoid fever, bacillary dysentery, giardia lamblia).
    • Vector-borne: Carried by ticks, mosquitoes, or fleas (West Nile virus, Lyme disease, Rocky Mountain spotted fever, malaria, Zika).
    • Direct Contact: Infections through direct contact (sexually transmitted diseases, infectious mononucleosis).

Immunity

  • Herd Immunity: Immunity in a community because most people are immune.
    • Levels vary; rubella needs 83-85%, pertussis needs 92-94% to be effective.
  • Natural Immunity: Immune system response with antibodies.
  • Acquired Immunity: Immune responses triggered by exposure to a disease.
  • Active Immunity: Production of antibodies in response to immunizations or infections; long-term.
  • Passive Immunity: Immunity provided through transfers of antibodies; short-term; can occur for vertical transmission as well as for horizontal.
    • Can transfer antibodies through the placenta or through transfusions, transfusions of immunoglobulins, plasma proteins, antitoxins.

Prevention and Control

  • Surveillance: Tracking and monitoring communicable diseases.
    • Collection and analysis of data, investigation of disease patterns.
    • Core functions of public health: Assessment, policy development, and assurance.
    • Asses newly emerging diseases such as COVID. policy about how to manage COVID or the measles or whatever is occurring and Assured the need providers and have the partners to implement prevention and control programs
    • Includes analyzing data, monitoring changes, and ensuring providers can implement prevention and control programs.
    • Identifies additional infected community members, determines the source of infection, and prevents further transmission.
    • Achieved through contact tracing.
      • Contact tracing: Identifying, assessing, and managing people exposed to a disease to prevent transmission. Infected people report names and contact information for anyone contact or close contact with and then the contacts can then be offered testing and treatment.
  • Nationally Notifiable Diseases: Mandated by state regulation to be reported from clinics, hospitals, etc., to the local public health department, then to the state.
    • Reporting to the CDC is voluntary.
    • The CDC recommends diseases to be reported to the state and helps states manage those diseases, but it's all voluntary. It is the state's responsibility to manage the diseases.
    • Contact tracing.

Levels of Prevention

  • Primary Prevention: Prevents the initial occurrence of disease.
    • Immunization, education about immunizations, education for travelers.
    • Promote basic first aid. In other words keeping wounds clean and infection free.
    • Elimination of risk such as; Hand hygiene, universal precautions, safe sex practices (promotion of condom use), advocating for clean water policies and community sanitation practices.
    • In the workplace besides good hand washing, maybe using proper personal protective equipment, the use of sharps containers, proper disposal of infectious material.
  • Secondary Prevention: Early detection and treatment of disease.
    • Screening for asymptomatic individuals (viral load for HIV, skin testing for tuberculosis).
    • Case finding (contact tracing with STIs, TB, COVID).
    • Quarantining or isolation.
  • Tertiary Prevention: Care and treatment of people with communicable disease to prevent complications and disabilities.
    • Providing antibiotics and treating the people.

Healthcare Goals

  • Reductions:
    • Infections from foodborne pathogens.
    • New diagnoses of HIV in sexually active adolescents and adults.
    • New AIDS cases.
    • Perinatally acquired HIV/AIDS cases.
    • HIV deaths.
    • Sexually transmitted infections.
    • Healthcare-associated infections.
    • Vaccine-preventable diseases.
    • Antibiotic courses for ear infections in young children (to prevent antibiotic resistance).
  • Increases:
    • Following safe food practices.
    • AIDS survival.
    • Testing for HIV in sexually active adolescents and adults, and people with TB.
    • Treatment of substance use; substance use treatment facilities that offer HIV/AIDS testing.
    • Use of condoms.
    • Immunization rates in children and adolescents.
    • Flu immunization in children and adults.
    • Adults immunized against pneumonias and shingles.
    • People with tuberculosis complete their therapy.