Health Promotion and Disease Prevention · 8 min read
Disease Prevention and Public Health
Communicable Disease Concepts
Communicable diseases (infectious diseases) are caused by pathogenic microorganisms and can spread from person to person or from environment to person.
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Categories of pathogens
Bacteria
Single-celled organisms; some cause disease (pathogenic), many are beneficial. Examples of bacterial diseases: strep throat, tuberculosis, Lyme disease, foodborne illness (Salmonella, E. coli). Treated with antibiotics; antibiotic resistance is growing concern.
Viruses
Non-living particles requiring host cells to replicate. Examples: influenza, common cold, COVID-19, HIV, hepatitis, herpes, HPV. Antibiotics ineffective; some antivirals available; vaccines prevent many viral diseases.
Fungi
Eukaryotic organisms including yeasts and molds. Examples of fungal infections: athlete's foot, ringworm, candidiasis, histoplasmosis. Treated with antifungal medications.
Parasites
Organisms living on or in host organism. Include protozoa (malaria, giardia), helminths (roundworms, tapeworms), ectoparasites (lice, scabies). Treatment varies by parasite type.
Prions
Misfolded proteins causing progressive neurological disease. Examples: Creutzfeldt-Jakob disease, mad cow disease. No treatment available; always fatal.
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Chain of infection
For communicable disease transmission to occur, six links must be present:
Infectious agent
The pathogen causing disease
Reservoir
Where pathogen lives and multiplies (humans, animals, environment)
Portal of exit
How pathogen leaves reservoir (respiratory secretions, blood, feces)
Mode of transmission
How pathogen travels to new host
Portal of entry
How pathogen enters new host (respiratory tract, mucous membranes, breaks in skin)
Susceptible host
Person vulnerable to infection
Breaking any link prevents transmission.
| Link | Action that breaks it |
|---|---|
| Infectious agent | Disinfecting surfaces, cooking food thoroughly |
| Reservoir | Treating infected people, controlling pests, safe food storage |
| Portal of exit | Covering coughs and sneezes |
| Mode of transmission | Handwashing, not sharing water bottles or personal items |
| Portal of entry | Bandaging wounds, gloves, not touching the face |
| Susceptible host | Vaccination, sleep, good nutrition |
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Modes of transmission
Direct contact
Person-to-person physical contact; includes sexual transmission
Indirect contact
Contact with contaminated objects (fomites)
Droplet transmission
Large respiratory droplets traveling short distances
Airborne transmission
Small particles remaining suspended in air
Vector-borne
Transmitted by insects or animals (mosquitoes, ticks)
Vehicle transmission
Transmitted through contaminated food, water, blood
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Body defenses against infection
First line (physical/chemical barriers)
Skin, mucous membranes, stomach acid, tears, saliva
Second line (innate immunity)
Inflammation, fever, phagocytes, natural killer cells
Third line (adaptive immunity)
Lymphocytes (B cells, T cells), antibodies, memory cells
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Immunization
- Vaccines stimulate adaptive immunity without causing disease. Types include:
- Live attenuated vaccines (MMR, varicella)
- Inactivated vaccines (polio IPV, hepatitis A)
- Subunit/conjugate vaccines (hepatitis B, HPV, pertussis)
- mRNA vaccines (COVID-19)
- Toxoid vaccines (tetanus, diphtheria)
Key Point
Herd immunity occurs when sufficient population proportion is immune, protecting those who cannot be vaccinated.Recommended immunization schedules exist for children, adolescents, and adults. School immunization requirements vary by state.
| Type | How it is acquired | Example |
|---|---|---|
| Naturally acquired active | Having the disease | Immunity after chickenpox |
| Artificially acquired active | Vaccination | Measles vaccine |
| Naturally acquired passive | Antibodies from the mother | Through the placenta or breast milk |
| Artificially acquired passive | Injected antibodies | Immune globulin after exposure |
Standard precautions
Treat all blood and body fluids as potentially infectious. Put on gloves before helping with a bloody nose or wound, use a barrier for rescue breaths, dispose of materials in a biohazard container and wash hands afterward.Noncommunicable Disease Concepts
Noncommunicable diseases (NCDs) are not transmissible between people. They typically develop over time and often share common risk factors.
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Major categories of NCDs
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Cardiovascular diseases
Heart disease
coronary artery disease, heart failure, arrhythmias
Stroke
ischemic (blocked blood vessel) or hemorrhagic (bleeding)
Hypertension
elevated blood pressure damaging blood vessels
Peripheral artery disease
reduced blood flow to limbs
Risk factors
tobacco use, physical inactivity, unhealthy diet, excessive alcohol, obesity, diabetes, high cholesterol, family history, age
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Cancer
- Uncontrolled cell growth forming tumors or spreading through blood/lymph
- Many types named for tissue of origin (lung, breast, colorectal, prostate, skin)
- Caused by genetic mutations from heredity, environmental exposures, lifestyle factors, infections, chance
- Risk factors vary by cancer type but include tobacco, alcohol, obesity, physical inactivity, certain infections (HPV, hepatitis), UV radiation, occupational exposures, family history
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Diabetes
Type 1
Autoimmune destruction of insulin-producing cells; requires insulin therapy
Type 2
Insulin resistance and relative insulin deficiency; most common form; strongly linked to obesity and lifestyle
Gestational
Develops during pregnancy; increases future Type 2 risk
Prediabetes
Elevated blood glucose not meeting diabetes criteria; reversible with lifestyle changes
Complications include cardiovascular disease, kidney disease, vision loss, neuropathy, amputations, infections
Low blood sugar at school
Shakiness, sweating, confusion or irritability in a student with diabetes can signal hypoglycemia. Follow the student's health plan: give about 15 grams of fast-acting carbohydrate (juice, glucose tablets) and recheck after 15 minutes. Never send the student to the office alone.5
Chronic respiratory diseases
Asthma
Chronic airway inflammation with episodic obstruction; triggers include allergens, irritants, exercise, infections
COPD (chronic obstructive pulmonary disease)
Progressive airflow limitation; includes emphysema and chronic bronchitis; primarily caused by smoking
Cystic fibrosis
Genetic condition affecting lungs and digestive system
| Quick-relief (rescue) | Long-term controller | |
|---|---|---|
| Purpose | Opens airways during symptoms | Reduces airway inflammation over time |
| When used | During an attack, or before exercise if prescribed | Daily, even without symptoms |
| Example | Albuterol inhaler | Inhaled corticosteroid |
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Other significant NCDs
- Chronic kidney disease
- Liver disease (cirrhosis, fatty liver disease)
- Neurological conditions (Alzheimer's, Parkinson's, epilepsy)
- Musculoskeletal conditions (arthritis, osteoporosis)
- Mental health conditions (depression, anxiety, schizophrenia)
- Autoimmune diseases (lupus, rheumatoid arthritis, multiple sclerosis)
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Modifiable risk factors common across NCDs
- Tobacco use
- Unhealthy diet
- Physical inactivity
- Harmful alcohol use
- Overweight and obesity
- Elevated blood pressure
- Elevated blood glucose
- Elevated cholesterol
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Non-modifiable risk factors
- Age
- Sex
- Genetics and family history
- Race/ethnicity (reflecting both genetics and social determinants)
| Modifiable | Nonmodifiable |
|---|---|
| Tobacco use and vaping | Age |
| Physical inactivity | Family history and genetics |
| Unhealthy diet | Sex |
| Excess alcohol use | Race and ethnicity |
| High blood pressure, cholesterol and blood sugar |
Public Health Principles and Practices
Public health focuses on preventing disease and promoting health at population level rather than individual clinical care.
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Core functions of public health
Assessment
Systematically collecting, analyzing, and disseminating information about community health status, needs, and resources
Policy development
Using scientific evidence to develop comprehensive public health policies and plans
Assurance
Ensuring necessary services are provided through direct provision, regulation, or partnership
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Essential public health services
- Monitor health status to identify community health problems
- Diagnose and investigate health problems and hazards
- Inform, educate, and empower people about health issues
- Mobilize community partnerships to solve health problems
- Develop policies and plans supporting health efforts
- Enforce laws and regulations protecting health
- Link people to needed personal health services
- Assure competent public and personal healthcare workforce
- Evaluate effectiveness, accessibility, and quality of services
- Research for innovative solutions
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Levels of prevention
Primordial prevention
Preventing risk factors from developing in populations (creating environments supporting healthy choices)
Primary prevention
Preventing disease before it occurs (vaccination, health education, safety legislation)
Secondary prevention
Detecting and treating disease early (screening programs, early diagnosis)
Tertiary prevention
Reducing impact of established disease (rehabilitation, chronic disease management)
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Epidemiology basics
Epidemiology is the study of distribution and determinants of health-related states in populations and application of this study to control health problems.
Key concepts:
Incidence
New cases occurring in population during specified time period
Prevalence
Total cases existing in population at specific time
Endemic
Constant presence of disease in population
Epidemic
Occurrence of disease exceeding normal expectancy
Pandemic
Epidemic spreading across countries or continents
Outbreak
Occurrence of cases in excess of normal, often localized
Worked example: incidence vs prevalence
A school of 800 students has 30 students with asthma at the start of the year, and 12 more are diagnosed during the year. Incidence counts only new cases: 12 ÷ 800 = 1.5% for the year. Prevalence counts all existing cases at a point in time: at year's end, (30 + 12) ÷ 800 = 42 ÷ 800 = 5.25%.5
Health disparities and health equity
- Health disparities are preventable differences in health outcomes among population groups. Factors contributing to disparities include:
- Race and ethnicity
- Socioeconomic status
- Geographic location
- Disability status
- Sexual orientation and gender identity
- Age
- Immigration status
- Social determinants of health are conditions in environments where people are born, live, learn, work, play, worship, and age that affect health outcomes. Categories include:
- Economic stability
- Education access and quality
- Healthcare access and quality
- Neighborhood and built environment
- Social and community context
Health equity means everyone has fair opportunity to attain their full health potential, with no one disadvantaged from achieving this potential because of social position or other socially determined circumstances.
| Domain | Example |
|---|---|
| Economic stability | Income, food security, housing |
| Education access and quality | Early childhood education, graduation |
| Health care access and quality | Insurance, a usual source of care |
| Neighborhood and built environment | Safe sidewalks, parks, clean air |
| Social and community context | Social support, discrimination, civic participation |
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Public health agencies and organizations
Local health departments
Direct service delivery, community assessment, emergency response
State health departments
Policy development, data collection, coordination, regulation
Centers for Disease Control and Prevention (CDC)
National disease surveillance, research, guidelines, emergency response
National Institutes of Health (NIH)
Biomedical research funding and conduct
Food and Drug Administration (FDA)
Drug, food, device safety regulation
World Health Organization (WHO)
International health coordination, standards, research
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Emergency preparedness
- Public health emergency preparedness involves planning, training, and exercising to respond to health emergencies including:
- Natural disasters (hurricanes, earthquakes, floods)
- Disease outbreaks and pandemics
- Bioterrorism
- Chemical and radiological emergencies
- Mass casualty events
- Key preparedness components: surveillance systems, laboratory capacity, communication systems, medical countermeasures, community resilience
Responding to a student who collapses
Check the scene and the student
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Call 911 and send for the AED
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Begin chest compressions: 100–120 per minute
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Use the AED as soon as it arrives
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Continue until EMS takes over
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