Introduction to infectious disease epidemiology

Transcription

1 Introduction to infectious disease epidemiology Mads Kamper-Jørgensen Associate professor, University of Copenhagen, Public health science 24 September 2013 Slide number 1

2 Practicals Elective English language course 10 ECTS, 30 face-to-face hours, work-load 270 hours 4-hour written PC exam relating to article, external evaluation, grading 7-scale Exam on January 14, 9 to 1 o clock Often 45 minute lecture and 90 minute lab Public health science 24 September 2013 Slide number 2

3 Aim Possess knowledge of frequent infectious diseases in Denmark Account for and calculate infectious disease frequency and association measures Be familiar with outbreak investigation, vaccination schedules, and infectious disease preparedness in Denmark Know of real world infectious disease epidemiologic work in Denmark Public health science 24 September 2013 Slide number 3

4 Material Textbook: Modern infectious disease epidemiology by Johan Giesecke, 2nd edition Absalon Homepage: Public health science 24 September 2013 Slide number 4

5 People Public health scientists, medical doctors, statistician Public health science 24 September 2013 Slide number 5

6 Schedule Date Teacher Subject Tuesday 24 September Tuesday 1 October Tuesday 8 October Tuesday 22 October Mads Kamper-Jørgensen, University of Copenhagen Anders Koch, Statens Serum Institut Trine Boysen, Rigshospitalet Kåre Mølbak, Statens Serum Institut Introduction to infectious disease epidemiology Frequency and association measures in infectious disease epidemiology Infectious diseases in Denmark Surveillance of infectious diseases in Denmark Tuesday 29 October Tuesday 5 November Tuesday 19 November Tuesday 26 November Tuesday 3 December Luise Müller, Statens Serum Institut Esben Budtz-Jørgensen, University of Copenhagen Tyra Krause, Statens Serum Institut Multiple, Statens Serum Institut Mads Kamper-Jørgensen, University of Copenhagen Infectious disease outbreaks in Denmark Statistical analysis of infectious disease data Vaccination schedules in Denmark Site visit at Statens Serum Institut Summary, evaluation and exam preparation Public health science 24 September 2013 Slide number 6

7 Why? The field is absent in this university s epidemiology curriculum, but widely used out there I wanted, but could not enroll for a similar course Infectious diseases historically were, and probably will again be, a major issue in Denmark Some analytical challenges and many terms are unique to infectious disease epidemiology Public health science 24 September 2013 Slide number 7

8 History Infectious disease epidemiology used to constitute epidemiology itself In 1500s Italy, Fracastoro was first to theorize regarding contagion of leprosy In mid 1800s Europe, Schleisner, Snow, Panum et al. drastically reduced tetanus, cholera, measles morbidity/mortality based on ideas of contagion using simple measures Public health science 24 September 2013 Slide number 8

9 History In late 1800s Europe, Koch, Henle, Pasteur et al. discovered the role of microorganisms, and overthrew the miasmatic (bad air) theory Prevention and treatment changed Western morbidity/mortality patterns from infectious to non-communicable. So populations grew In late 1900s Western world infectious diseases including AIDS, SARS, avian flu, West Nile virus, TB emerge because of new pathogens, drug resistance etc. Public health science 24 September 2013 Slide number 9

10 Analytical challenges A case may also be a risk factor People may be immune A case may be a source without recognizing it Contact patterns, vaccination Therefore dependency between observations Violation of a key assumption of most statistical models Often times limited samples size Sometimes a need for urgency Public health science 24 September 2013 Slide number 10

11 Quiz Under the headline Quizzes, click 24 September 2013 Public health science 24 September 2013 Slide number 11

12 Disease terms Infectious: caused by microorganisms Communicable: transmission from person to person Transmissible: transmission through unnatural routes Contagious: highly infectious Public health science 24 September 2013 Slide number 12

13 Exposure outcomes Public health science 24 September 2013 Slide number 13

14 Emics Epidemic: Incidence with a frequency clearly in excess of normal expectancy Pandemic: epidemic spread across large regions Endemic: Steady incidence over a longer period Public health science 24 September 2013 Slide number 14

15 Time periods Incubation period: from infection until he/she develops symptoms Infectious period: during which a person can transmit a disease Latent period: from infection until infectious period starts Public health science 24 September 2013 Slide number 15

16 Rates Case-fatality rate: proportion of clinically infected who die. Sometimes expressed in relation to time Attack rate: proportion of exposed who become clinically infected. Often excludes immune Basic reproductive rate (R 0 ): average number of individuals directly infected by a case during his/her entire infectious period, in a susceptible population R 0 <1, the disease will eventually disappear R 0 =1, the disease will become endemic R 0 >1, the disease will become epidemic The above are not true rates Public health science 24 September 2013 Slide number 16

17 R 0 depends on When the exact transmission pattern is unknown, R 0 can be approximated by R 0 = β x κ x D β = risk of transmission per contact = the attack rate κ = number of contacts D = duration of infectious period Very difficult to obtain good input data Public health science 24 September 2013 Slide number 17

18 Zombies Principles of infectious disease epidemiology using a bloody case Public health science 24 September 2013 Slide number 18