CHAPTER 11 AND 12 <3

• Epidemiology


  The study of factors that determine the frequency, distribution, and determinants of diseases in human populations, and ways to prevent, control, or eradicate diseases in populations
• Pathology


  The study of the structural and functional manifestations of disease and is involved in diagnosing diseases in individuals
• Epidemiologists are scientists who specialize in the study of disease and injury patterns (incidence and distribution patterns) in populations and ways to prevent or control diseases and injuries
• Educational backgrounds of epidemiologists

  • Physicians with specialization in epidemiology or public health
  • Doctor of Philosophy (PhD or DPhil)
  • Master of Science or Master of Public Health (MS or MPH)
  • Bachelor of Science (e.g., RN or BSN) plus specialized training in epidemiology
• Communicable disease


  An infectious disease that is transmissible from one human to another (i.e., person to person)
• Contagious disease


  A communicable disease that is easily transmitted from one person to another
• ID50


  The infective dose that it takes to infect 50% of a population
• LD50


  The lethal dose that results in the death of 50% of the population
• Zoonotic diseases


  Infectious diseases that humans acquire from animal sources
• Incidence


  The number of new cases of a disease in a defined population during a specific time period
• Morbidity rate


  The number of new cases of a particular disease that occurred during a specified time period and per a specifically defined population (usually per 100,000 population)
• Period prevalence


  The number of cases of a disease existing in a given population during a specific time period
• Point prevalence


  The number of cases of a disease existing in a given population at a particular moment in time
• Mortality rate


  The ratio of the number of people who died of a particular disease during a specified time period per a specified population (usually per 1,000, 10,000, or 100,000 population)
• Sporadic disease


  A disease that occurs only rarely and without regularity (sporadically) within the population of a particular geographic area
• Endemic disease


  A disease that is always present within a population
• Epidemic disease


  A disease that occurs in a greater than usual number of cases in a particular region and usually occurs within a relatively short period of time
• Pandemic disease


  A disease that occurs in epidemic proportions in many countries simultaneously— sometimes worldwide
• Waterborne disease outbreaks occur annually in the United States, associated with both drinking water (referred to as "potable") and water that is not intended for drinking (referred to as "nonpotable" or "recreational water")
• It is estimated that there are approximately 48 million cases of foodborne illnesses in the United States each year, but only about 10 million have an etiologic agent identified and reported to health authorities
• HIV/AIDS, TB, and malaria cause more than 300 million illnesses and more than 5 million deaths per year
• The AIDS epidemic began in the United States around 1979, but the epidemic was not detected until 1981. It was not until 1983 that HIV—the virus that causes AIDS—was discovered
• HIV has claimed more than 35 million lives over the past three decades. The total number of people living with HIV worldwide in 2015 was estimated to be 36.7 million. Almost 70% of people living with HIV are in sub-Saharan Africa
• In 2016, an estimated 39,782 people in the United States were diagnosed with HIV infection. Since the epidemic began, it is estimated that over 1.2 million people in the United States have been diagnosed with AIDS
• An estimated 1.1 million people in the United States are currently living with HIV infection. One in seven of those people are unaware of their infection
• Components in the chain of infection

  • Pathogen
  • Reservoir of infection
  • Portal of exit
  • Mode of transmission
  • Portal of entry
  • Susceptible host
• Reservoir of infection


  Living hosts or inanimate objects or materials where a pathogen can survive and multiply
• Zoonoses


  • Rabies
  • Toxoplasmosis
  • Tuberculosis
• Carrier


  A person who is colonized with a particular pathogen, but the pathogen is not currently causing disease in that person (asymptomatic)
• Arthropods


  Insects (e.g., mosquitoes, biting flies, lice, and fleas) and arachnids (e.g., mites and ticks) that serve as reservoirs of infection
• Malaria is the fifth leading cause of death from infectious diseases worldwide (after respiratory infections, HIV/AIDS, diarrheal diseases, and TB)
• About half the world's population (3.3 billion people) live in areas at risk of malaria transmission in 109 countries and territories. A total of 35 countries (30 in sub-Saharan Africa and 5 in Asia) account for 98% of global malaria deaths
• Zoonotic diseases (zoonoses)


  Infectious diseases that humans acquire from animal sources
• The tick is now infected with Borrelia burgdorferi, the spirochete that causes Lyme disease
• Fomites


  Inanimate objects or materials that can serve as a reservoir of infection
• About half the world's population (3.3 billion people) live in areas at risk of malaria transmission in 109 countries and territories
• A total of 35 countries (30 in sub-Saharan Africa and 5 in Asia) account for 98% of global malaria deaths
• Fomites


  Inanimate objects capable of transmitting pathogens
• Fomites found within health care settings include patients' gowns, bedding, towels, eating and drinking utensils, and hospital equipment, such as bedpans, stethoscopes, latex gloves, electronic thermometers, and electrocardiographic electrodes, which become contaminated by pathogens from the respiratory tract, intestinal tract, or the skin of patients
• A hospital staphylococcal epidemic may begin when aseptic conditions are relaxed and when a Staphylococcus aureus carrier transmits the pathogen to susceptible patients (e.g., babies, surgical patients, debilitated persons)