1. Infectious Disease Epidemiology, Module I Introduction

2. 9/22/00ANN JOLLY 2 Introduction n Round table n Your expectations of this day n Your career goals n Knowledge base n Why is infectious disease epidemiology important?

3. 9/22/00ANN JOLLY 3 General goals n Understand the infectious disease process n Identify transmission routes, modes, media and reservoirs n Understand public health law u Understand infectious disease surveillance u Understand the process of outbreak investigation

4. 9/22/00ANN JOLLY 4 What causes disease? Agent Host Environment BacteriaVirusesFungi Parasite s Prions HousingFood Water qualityAir quality AgeGender Ethnic group LifestyleSocioeconomic

5. 9/22/00ANN JOLLY 5 Exposure Infection Disease, symptomatic/ asymptomatic Carrier Convalescent Sequelae Infectious disease process

6. 9/22/00ANN JOLLY 6 What determines infection? n (other than exposure) n The deposition, colonisation and multiplication of an organism in a host, n Usually accompanied by an immune response n May occur with or without clinical illness

7. 9/22/00ANN JOLLY 7 Predictors of infection AGENT HOST ENVIRONMENT Immunity Race Age Gender Socioeconomic Living Conditions Social Climate Dose Genetics Hardiness Communicability

8. 9/22/00ANN JOLLY 8 Infectious disease process - Source n Reservoirs u human u insect u animal n Medium u air borne u water borne u food borne u blood borne u genital

9. 9/22/00ANN JOLLY 9 Infectious disease process - Transmission n Route u direct F Oral, oral/faecal F sexual F respiratory - droplets or droplet nuclei 1-5m F parenteral F congenital u indirect F vector F vehicle

10. 9/22/00ANN JOLLY 10 Infectious disease process - Infection & Incubation n Infection u dose u infectivity u hardiness u rate of replication n Incubation u infectiousness u immune response u intervention

11. 9/22/00ANN JOLLY 11 Infectious disease process - Disease n Disease u signs, symptoms u asymptomatic u infectious n Outcome/Prognosis u morbidity u mortality u sequelae u recovery F infectious (chronic carrier)

12. 9/22/00ANN JOLLY 12 Diagnosis n Clinical u based on signs, symptoms n Laboratory confirmed u microbiology F detection F isolation u serology u parasitology u virus

13. 9/22/00ANN JOLLY 13 Diagnostic process n Patient presents u due to symptoms u case - finding F screening F active investigation of contacts

14. 9/22/00ANN JOLLY 14 Laboratory diagnosis n Lab tests ordered u Method of collection, site, volume u Right tests ordered F correct organisms F antimicrobial sensitivity u Sent to the right place u In the right media u Transport conditions F Time F Temperature

15. 9/22/00ANN JOLLY 15 Laboratory diagnosis, (cont.) n Routine identification of organisms causing diarrhoea n C & S u shigellae u salmonellae u yersinia u aeromonas u campylobacter n In children < 5 in the summer u Vertoxigenic E. coli

16. 9/22/00ANN JOLLY 16 Laboratory diagnosis, (cont.) n If food-borne is suspected and written on the requisition u staph aureus u bacillus cereus u clostridium perfringens

17. 9/22/00ANN JOLLY 17 Interpretation of tests, if positive n Test sensitivity u % of people accurately diagnosed as ill of all people tested n Normal flora? u N. meningitidis u Streptococcus pyogenes n Carrier state n Contamination during collection n Lab. Error n Multiple infections

18. 9/22/00ANN JOLLY 18 Interpretation of tests, if negative n Prior antibiotic therapy n Problems in u collection F timing F site u storage u transport u media n Failure to incubate long enough

19. 9/22/00ANN JOLLY 19 Summary n Infectious disease process u reservoir - transmission - disease/death n Determinants of infection u agent, host, environment interaction

20. 9/22/00ANN JOLLY 20 Next Steps n Future applied u disease in populations F surveillance F outbreaks