Disease and epidemiology

• Pathology


  The study of a disease
• Etiology


  The study of the cause of a disease

  
• Pathogenesis


  The development of a disease
• Infection


  Invasion and colonization of the body by pathogens
• Disease


  An abnormal state in which the body is not functioning normally
• Normal Microbiota


  • Transient microbiota may be present for days, weeks, or months
  • Normal microbiota permanently colonize the host

  
• Symbiosis


  The relationship between normal microbiota and the host
• Pathology


  The study of a disease
• Types of Symbiosis


  • Commensalism (one organism benefits, the other is unaffected)
  • Mutualism (both organisms benefit)
  • Parasitism (one organism benefits at the expense of the other)
• Etiology


  The study of the cause of a disease

  
• Some normal microbiota are opportunistic pathogens
• Pathogenesis


  The development of a disease
• Normal Microbiota Protect the Host

  • Occupying niches that pathogens might occupy
  • Producing acids and competing for nutrients
  • Producing bacteriocins or antibiotics against invading microbes
• Infection


  Invasion and colonization of the body by pathogens
• Probiotics


  Live microbes applied to or ingested into the body, intended to exert a beneficial effect
• Disease


  An abnormal state in which the body is not functioning normally
• Koch's Postulates


  • The same pathogen must be present in every case of the disease
  • The pathogen must be isolated from the diseased host and grown in pure culture
  • The pathogen from the pure culture must cause the disease when it is inoculated into a healthy, susceptible laboratory animal
  • The pathogen must be isolated from the inoculated animal and must be shown to be the original organism

  
• Normal Microbiota


  • Transient microbiota may be present for days, weeks, or months
  • Normal microbiota permanently colonize the host
• Communicable disease


  A disease that is spread from one host to another

  
• Symbiosis


  The relationship between normal microbiota and the host
• Contagious disease


  A disease that is easily spread from one host to another
• Types of Symbiosis


  • Commensalism (one organism benefits, the other is unaffected)
  • Mutualism (both organisms benefit)
  • Parasitism (one organism benefits at the expense of the other)
• Noncommunicable disease


  A disease that is not transmitted from one host to another

  
• Some normal microbiota are opportunistic pathogens
• Normal Microbiota Protection


  • Occupying niches that pathogens might occupy
  • Producing acids and competing for nutrients
  • Producing bacteriocins or antibiotics against invading microbes
• Incidence


  Fraction of a population that contracts a disease during a specific time
• Probiotics


  Live microbes applied to or ingested into the body, intended to exert a beneficial effect
• Prevalence


  Fraction of a population having a specific disease at a given time
• Koch's Postulates


  • The same pathogen must be present in every case of the disease
  • The pathogen must be isolated from the diseased host and grown in pure culture
  • The pathogen from the pure culture must cause the disease when it is inoculated into a healthy, susceptible laboratory animal
  • The pathogen must be isolated from the inoculated animal and must be shown to be the original organism

  
• Sporadic disease


  Disease that occurs occasionally in a population
• Communicable disease


  A disease that is spread from one host to another
• Endemic disease


  Disease constantly present in a population
• Contagious disease


  A disease that is easily spread from one host to another
• Epidemic disease


  Disease acquired by many hosts in a specific area in a short time
• Noncommunicable disease


  A disease that is not transmitted from one host to another

  
• Pandemic disease


  A worldwide epidemic
• Incidence


  Fraction of a population that contracts a disease during a specific time
• Herd immunity


  Immunity in most of a population
• Prevalence


  Fraction of a population having a specific disease at a given time
• Factors affecting interactions between pathogens, hosts, and environments

  • Factors about the pathogen (virulence, portal entry, number of organisms)
  • Factors about the host (health status, nutritional status, susceptibility)
  • Factors about the environment (physical factors, reservoirs, sanitary conditions, water availability)