Microbiology

• Epidemiology


  The study of the determinants, occurrence, distribution and control of health and disease within a population
• Epidemiology


  1. Observe

  2. Hypothesize

  3. Test

  4. Evaluate
• Endemic disease


  Occurs with a steady, low level frequency at moderately regular intervals within a population
• Predictable diseases


  • Cold (rhinovirus)
• Sporadic disease


  Occurs occasionally at irregular intervals
• Unpredictable diseases


  • Tetanus (Clostridium tetani)
• Epidemic


  Sudden increase in the incidence of a disease beyond the expected level
• Epidemic


  • Malaria
• Pandemic


  Sudden increase in the incidence of a disease beyond the expected level within a large population covering a wide area (global!)
• Pandemic


  • Spanish flu
• Outbreak


  Sudden unexpected occurrence of a disease either locally or within a limited section of a population
• Zoonoses


  Animal diseases that can be occasionally transmitted to human hosts
• Zoonoses


  • Anthrax (Bacillus anthracis)
• Prior to 1900's infectious diseases were the major killer of humans
• Humans did not live long enough to suffer significantly from many of the diseases of an ageing population that we see today
• Major infectious diseases prior to 1900


  • Smallpox
  • Cholera
  • Typhoid fever
  • Yellow fever
  • Bubonic plague
  • Measles
  • Whooping cough
  • Scarlet fever
  • Diphtheria
• John Snow


  • Established link between consumption of contaminated water and cholera
  • Established basic principles of epidemiological investigation
• Epidemiological investigation


  1. Collect information

  2. Analyse information

  3. Act!

  4. Evaluate
• The General Board of Health Report 1854 dismissed the link between contaminated water and cholera
• The Lambeth Company did not move their water source upstream, resulting in 70 deaths per 10,000 houses
• The Southwark and Vauxhall Company moved their water source upstream, resulting in 5 deaths per 10,000 houses
• Vibrio cholerae


  • Gram negative
  • Facultatively aerobic
  • Fermentative
  • Oxidase positive
  • Motile by polar flagella
  • Aquatic
  • Phage-encoded toxin
• Morbidity data


  Measurement of the incidence and prevalence of a disease within a population
• There is a legal requirement to notify UKHSA (formally Public Health England) when certain infections are detected
• Notifiable infections


  • Cholera
  • Tuberculosis
  • Meningitis
  • COVID
• Incidence


  Newly diagnosed cases in a certain time
• Prevalence


  Frequency of disease in population in a certain time
• Influenza has 650,000 annual mortality (2017)
• 2019-nCoV had 132 deaths from 6065 cases (29/1/20)
• Immunological surveys


  Screen population to detect individuals who have mounted an immune response to a particular pathogen (humoral or CMI) or to directly detect the presence of pathogens
• Use of antibiotics and other pharmaceuticals


  Suggests the presence of various organisms (Broad spectrum vs Narrow spectrum)
• Population demographics


  Age profiles, ethnic makeup etc. can influence disease prevalence
• Epizootology


  Monitoring animal diseases that can be passed on to humans
• Ecological studies of vectors


  Prevalence of arthropods in specific environments can define the risk of arthropod-borne diseases
• Arthropod-borne disease


  • Dengue fever - more active in hot weather when mosquitoes are more prevalent
• Centralisation of epidemiological information


  World Health Organisation (WHO), Centers for Disease Control and Prevention (CDC), Health Protection Agency (HPA), European Centre for Disease Prevention and Control (ECDC)
• The WHO, CDC, HPA, and ECDC collect, correlate and disseminate epidemiological information
• The WHO Disease Outbreak News (DONs) site reports on current virus infections causing concern
• Many factors contribute to current cholera outbreaks globally
• The WHO Global Health Observatory provides access to WHO datasets on various health topics