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Systems innate immune system humoral

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Unformatted text preview: enEficaEon of causes of new, emerging infecEons e.g. HIV, SARS •  Surveillance of infecEous disease •  IdenEficaEon of source of outbreaks •  Studies of routes of transmission and natural history of infecEons •  IdenEficaEon of new intervenEons Epidemiologic Triad Disease is the result of forces within a dynamic system consisting of: "  "  "  agent of infection host environment Factors Influencing Disease Transmission Agent Environment •  Weather •  InfecFvity •  Housing •  Pathogenicity •  Geography •  Virulence •  OccupaFonal seQng •  Immunogenicity (ability to indice an immune response in host) •  Air quality •  Food •  AnFgenic stability (e.g. stability of pathogen proteins in host) •  Survival •  Age •  Sex Host •  Genotype •  Behaviour •  NutriFonal status •  Health status Epidemiologic Triad-Related Concepts Infectivity (ability to infect) (number infected / number susceptible) x 100 Pathogenicity (ability to cause disease) (number with clinical disease / number infected) x 100 Virulence (ability to cause death) (number of deaths / number with disease) x 100 All are dependent on host factors infecEvity depends on the number of infecEous parEcles required (viral parEcles, bacterial cells) •  higher infecEvity = higher secondary infecEons (infected person infecEng other people), e.g. –  tuberculosis = low infecEvity –  smallpox = high infecEvity bioterrorism.slu.edu/bt/products/bio_epi/ scripts/mod3.pdf pathogenicity •  ability of the pathogen (microbe) to cause disease once an infecEon has been established •  for diseases with high pathogenicity if you have an infecEon you almost always have the disease (experience symptoms); some diseases have relaEvely low pathogenicity –  smallpox = high pathogenicity –  polio = low pathogenicity –  hOp://www.health.ny.gov/diseases/communicable/poliomyeliEs/fact_sheet.htm –  "Up to 95 percent of people infected with polio have no symptoms. However, infected persons without symptoms can sEll spread the virus and cause others to develop polio. About four to five percent of infected people have minor symptoms such as fever, muscle weakness, headache, nausea and vomiEng. One to two percent of infected persons develop severe muscle pain and sEffness in the neck and back. Less than one percent of polio cases result in paralysis." bioterrorism.slu.edu/bt/products/bi...
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