SARS Epidemiology for Public Health Action

Transcription

1 SARS Epidemiology for Public Health Action Aileen J Plant on behalf of The Global Network for SARS Epidemiology With thanks to Angela Merianos, Angus Nicoll and all the SARS epidemiology people around the globe!

2 SARS A triumph for networks!

3 Today Brief description of epidemiology (Who? When? Where? Why? How?) Epidemiology for public health action Highlight the unknown The challenges ahead

4 The initial challenge No name No clear-cut clinical diagnosis No test No idea of clinical course No idea of long term implications Not much idea how it spread When does infectiousness start? When does infectiousness finish? Is there any short term immunity? Is there any long term immunity?

5 Notifications of SARS to WHO by week (21 March-13 June, 2003) Incubation period Infectious period Case fatality ratios Reproduction number Routes of transmission and exposure dose 0 21-Mar 28-Mar 4-Apr 11-Apr 18-Apr 25-Apr 2-May 9-May 16-May 23-May 30-May 6-Jun 13-Jun Sub-clinical infection Source: Reservoirs eg animals

6 Incubation period imprecise but reasonably consistent Canada China Hong Kong SAR Singapore Vietnam WHO Europe 2 0 Minimum Mean Maximum

7 Transmission evidence Asymptomatic Mild symptoms Sick Recovering?? Quality of evidence Infectiousness X Y YYY X

8 Case fatality ratios crude estimates Apr 18-Apr 25-Apr 2-May 9-May 16-May 23-May 30-May 6-Jun 13-Jun Percentage Vietnam Hong Kong Singapore Canada China Taiwan Province

9 Routes of tranmission All the evidence in favour of close contact Mostly <1 metre Fomites can not be excluded BUT not much evidence of prolonged risk in spite of microbiological findings Aerosol is not likely Amoy Gardens???

10 Cumulative percentage of SARS cases by country and time Vietnam Hong Kong Singapore Canada China Taiwan Province Percentage 28-Feb 7-Mar 14-Mar 21-Mar 28-Mar 4-Apr 11-Apr 18-Apr 25-Apr 2-May 9-May 16-May 23-May 30-May 6-Jun 13-Jun

11 Health Care Workers and SARS HCW Hong Kong SAR 58% (early report Lee et al) Vietnam 53% Sick health care workers matter for SARS but they matter far more for the rest of the health system

12 SARS Vietnam: clinical attack rates by occupational risk groups Hospital A % Any doctor 16 Any nurse 35 Administration staff 2 Other staff with patient contact 53 Outside staff 0 Total hospital 18 Concurrent patients NOT 7 admitted for SARS Hospital B 0 Contacts of one well-tracked 6 (and friendly!) case

13 Conclusions the challenges ahead MUST have sufficient: clinical diagnostic skills laboratory capacity surveillance capacity response capacity plans of action infection control applied research capacity

14 Conclusions There is a lot of epidemiological work to be done But the good news is We don t have to wait for perfect answers to control SARS, we can do it now!

15 Photo: Dr Joel Montgomery, WHO SARS Team, Vietnam

16 Mean age and SARS Hong Kong SAR Hong Kong SAR (Amoy Gardens) Vietnam 39.3 (n = 156, Lee et al) 39.8 (n = 75, Peiris et al) 40.8 (n = 62, unpub)

17 SARS Vietnam: Feb-Mar 2003 No of cases by date of onset the incubation period Maximum-minimum incubation period (5 days) 10 Median IP (6-7 days) Index case admitted Feb 22 Feb 24 Feb 26 Feb 28 Mar 2 Mar 4 Mar 6 Mar 8 Mar 10 Mar 12 Mar 14 Mar 16 Mar 18 Mar 20 Mar 22 Mar 24 Mar 26 Mar 28 Mar 30 Apr 1 Apr 3 Apr 5 Apr 7 No of cases Max IP (10 days)

18 Infection control - it matters! Infection control strengthened Maximum incubation period 10 Floor of hospital isolated Feb 22 Feb 24 Feb 26 Feb 28 Mar 2 Mar 4 Mar 6 Mar 8 Mar10 Mar 12 Mar 14 Mar 16 Mar 18 Mar 20 Mar 22 Mar 24 Mar 26 Mar 28 Mar 30 Apr 1 Apr 3 Apr 5 Apr 7 Number of cases HCW Other No of cases by date of onset of symptoms, Vietnam