Epidemiology Fundamentals

Epidemiology

• Study of disease, focusing on factors that determine frequency, distribution, and determinants of diseases in human populations
• Epidemiologists develop ways to prevent, control, or eradicate diseases in populations

Types of Diseases

• Communicable disease: infectious disease that can be transmitted from one person to another
• Contagious disease: communicable disease that is easily transmitted from person-to-person
• Zoonotic disease: disease that humans acquire from animal sources

Disease Measures

• Incidence: number of new cases of a disease in a defined population during a specific time period
• Morbidity rate: number of new cases of a disease per a specifically defined population (usually per 1,000, 10,000, or 100,000) during a specified time period
• Prevalence: number of cases of a disease existing in a given population during a specific time period
  • Period prevalence: number of cases during a specific time period (e.g., during the year 2006)
  • Point prevalence: number of cases at a particular moment in time
• Mortality rate: ratio of number of people who died of a particular disease during a specified time period per a specified population

Disease Occurrence

• Sporadic disease: disease that occurs only occasionally within a particular geographic area (e.g., tetanus)
• Endemic disease: disease that is always present within the population of a particular geographic area (e.g., gonorrhea)
• Epidemic disease: greater than usual number of cases of a disease in a particular region, usually within a short period of time (e.g., Legionnaires disease epidemic of 1976)
• Pandemic: disease that is occurring in epidemic proportions in many countries simultaneously (e.g., Influenza, HIV/AIDS, Tuberculosis, Malaria)

Biological Warfare and Bioterrorism

• Biological warfare (BW) agents: use of microorganisms in times of war
• Bioterrorism agents: use of microorganisms to create fear, chaos, illness, and death
• Four most likely potential agents: Bacillus anthracis, Clostridium botulinum, Smallpox virus (Variola major), and Yersinia pestis

Water and Sewage Treatment

• Rural and suburban areas: septic tanks
• Urban areas: wastewater treatment plants
• Primary sewage treatment: physical process
• Secondary sewage treatment: biological process
• Tertiary sewage treatment: additional treatment steps
• Chlorination: bleaching and disinfection
• Filtration: using fine sand and charcoal
• Distillation: purification process
• Major steps in water treatment:
  • Sedimentation (settling)
  • Coagulation (flocculation)
  • Filtration
  • Chlorination