Chapter 6

• Types of diseases

  • Infectious diseases
  • Non-infectious diseases

  
• Infectious diseases


  Can be transmitted from one individual to another, diseases caused by pathogenic agent

  
• Infectious diseases

  • Pneumonia
  • Influenzas
  • Cholera
  • Tuberculosis
• Non-infectious diseases


  Cannot be transmitted via environment to one individual to another, diseases caused by environmental, nutritional and inherited factors
• Non-infectious diseases

  • Genetic
  • Cardiovascular
  • Cancer
• Emerging and re-emerging diseases

  • Emerging disease
  • Re-emerging disease
• Emerging disease


  New or previously unrecognised disease, diseases that have increased in incidence or virulence, diseases that may increase in near future
• Re-emerging disease


  Disease that reappears after significant decline in incidence, once controlled diseases but increased at a rate that causes health issues, usually increasing incidence of drug resistant pathogens
• Infectious diseases are caused by viruses, bacteria, parasites or other pathogens
• Zoonotic disease


  Another animal to human
• Factors that influence emergence of diseases

  • Human demographics
  • Human behaviour
  • Changes in farming practises and food production
  • Uncontrolled or inappropriate use of antimicrobials
  • Lack of sanitation and poor hygiene
• Patterns of diseases

  • Endemic
  • Outbreak
  • Epidemic
  • Pandemic

  
• Endemic


  Diseases present at constant low levels in population/region
• Outbreak


  Diseases of sudden increased prevalence in local level
• Epidemic


  Infectious disease increased rapidly at a national level
• Pandemic


  Infectious disease increased rapidly to a worldwide level
• Most diseases in this case are likely to be infectious, but can also be non-infectious (e.g, obesity)
• Pandemics are global outbreaks of disease
• How pandemics occur

  1. A pathogen (new or novel strain) suddenly appears

  2. Occurs in geographic areas where populations have not been exposed to before

  3. People have little to no immunity

  4. No vaccine or limited quantities of vaccine available
• Ways of pandemic transmission

  • Airborne particles -> coughed or sneezed by an infected person
  • Blood or other bodily fluids of an infected person
  • Vectors -> living organisms that transmit infection (mosquitoes, fleas etc.)
• Epidemic


  Outbreaks in communities or restricted geographical regions

  
• Factors that influence immunity of indigenous people

  • No previous exposure to pathogens -> no immunological memory
  • Route of transmission
  • High population density -> easily transmissible
  • Prior health and nutritional status
  • Intergroup social relationships
• Methods of identifying bacteria

  • Phenotypic method
  • Genotypic/molecular methods
  • Immunological method

  
• Phenotypic method


  Identifies bacteria through traits
• Phenotypic method

  1. Microscopy -> determine structure of bacteria/response to gram stain

  2. Growing bacteria on different media -> shows bacterial growth patterns

  
• Genotypic/molecular methods

  Identifies bacteria through genome sequencing
• Genotypic/molecular methods

  1. Gene probes -> radioactive nucleic acids that binds to specific genes

  2. DNA sequencing

  3. Plasmid fingerprinting -> DNA profiling techniques

  
• Immunological method


  Detects presence of specific bacteria
• Immunological method

  1. Monoclonal antibodies -> target and bind to specific bacterial antigen

  2. ELISA

  3. Immunofluorescence -> antibody with fluorescent marker binds to specific antigen

  
• Reservoirs/host


  • Humans
  • Animals
  • Environment
• Host


  Organism that gets a disease
• Reservoir


  Where a pathogen grows and replicates
• Factors affecting host susceptibility

  • Genetic factors
  • Specific immunity
  • Sex
  • Age
  • Nutrition
• Modes of transmission

  • Direct
  • Indirect
  • Vectors
• Direct transmission


  Person to person
• Indirect transmission

  Airborne particles, contamination, ingestion
• Vector transmission


  Pathogenic agents that spread disease
• Incubation period


  Interval between the person's first exposure to symptoms
• Methods of disease control

  • Prevention
  • Vaccination
  • Medication
  • Surveillance
  • Vector control
  • Control standards

  
• Prevention


  Change in behaviours such as good hygiene and sanitation