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Communicability Patient factors
Not infectious prior to symptoms Increases with increased severity of disease Increases post-onset symptoms (peak at day
7-10) Not infectious after recover No evidence of prolonged carriage or relapse
Setting Duration, degree of contact Contact with airway (?contact with stool)
Communicability: time in disease course
Peiris et al. Lancet, 2003
NPA / TNS N=392
Onset (days)
0 – 23 – 56 – 8
9 – 1112 – 1415 – 1718 – 2021 – 23
% positive
3143605759351813
PCR: Time to positive
%positive
0578690
100336043
Stools N=50
Public Health - Hong Kong May 2003
Communicability Patient factors
Not infectious prior to symptoms Increases with increased severity of disease Increases post-onset symptoms (peak at day
7-10) Not infectious after recover No evidence of prolonged carriage or relapse
Setting Duration, degree of contact Contact with airway (?contact with stool)
Exposure Risk in ICU Loeb et al. (ICAAC 2003)
8/32 entering room vs 0/11 others (P=0.09) Risks: assisting with intubation RR=4.2 (1.6, 11) suctioning prior to intubation RR=4.2 (1.6,11) manipulation O2 mask RR=9.0 (1.3,65)
• Scales et al. (ICAAC 2003)- 6/31 entering room vs. 1/38 others RR=8.8 (1,420)- Risks: in room for >4 hrs RR=24 (1.2,311) present >30min with NIV RR=105 (3,3000)
SARS Control
Identification of cases Isolation/quarantine
IP
Varia et al. CMAJ 2003
Toronto Area Probable and Suspect cases by source of infectionMay 5, 2003
0
2
4
6
8
10
1223
-Feb
-03
25-F
eb-0
327
-Feb
-03
01-M
ar-0
303
-Mar
-03
05-M
ar-0
307
-Mar
-03
09-M
ar-0
311
-Mar
-03
13-M
ar-0
315
-Mar
-03
17-M
ar-0
319
-Mar
-03
21-M
ar-0
323
-Mar
-03
25-M
ar-0
327
-Mar
-03
29-M
ar-0
331
-Mar
-03
02-A
pr-0
304
-Apr
-03
06-A
pr-0
308
-Apr
-03
10-A
pr-0
312
-Apr
-03
14-A
pr-0
316
-Apr
-03
18-A
pr-0
320
-Apr
-03
22-A
pr-0
324
-Apr
-03
26-A
pr-0
328
-Apr
-03
30-A
pr-0
302
-May
-03
04-M
ay-0
3
Date of onset of first symptoms
Nu
mb
er
of
ca
se
s (
P &
S)
Travel
Non health care
Health care settings
PPP
ATM
Outpatient
Entrance
Drug Store Emergency
EntranceSecurity Emergency
Registration
Emergency
Nurse
Admitting
Vending
Machines
Waiting Room
Trauma
Room
Room 1
Room 2
Room 3
Room 4
Room 5
Room 6
Stock
Room
Room 7
Room 8
Room 9
Eye Room
Fracture
Room
Soiled
Linen
Show er
W CW C
Observation Room
Nursing Station
Ante
Room
Bed 1
Bed 2
Bed 3
Bed 4
Bed 5
Bed 6
Bed 1 Bed 2 Bed 3
Bed 4 Bed 5
Bed 8 Bed 7 Bed 6
Bed 1
Bed 2Bed3
Grace DivisionEmergency DepartmentMarch 16; 22:45-23:30
Reported cases of SARS in cases linked to the BLD group
March 20 to April 16, 2003
0
1
2
3
4
5
6
7
8
19/0
3/03
21/0
3/03
23/0
3/03
25/0
3/03
27/0
3/03
29/0
3/03
31/0
3/03
02/0
4/03
04/0
4/03
06/0
4/03
08/0
4/03
10/0
4/03
12/0
4/03
14/0
4/03
16/0
4/03
Date of onset of symptoms
Nu
mb
er
of
ca
se
s
Health Care WorkerBLD
Family
Mr. S Jr.
Church meetings Funeral
Cluster of SARS in HCWs 54 y.o.m. physician
April 1-2 saw 3 patients from BLD community
April 4-5 became ill April 12 admitted to ICU
April 13 Intubated RT-PCR positive in sputum and stool
April 15-21 9 HCW become ill including 6 involved with
intubationMMWR 2003 May 16
0
2
4
6
8
10
12
April May June
Household
Hospital
Effectiveness of Precautions
Seto et al. Lancet 2003: Case (n=13)/Control (241) Lower risk with handwashing OR 0.2 (.07,1) Lower risk with gloves OR 0.5 (.14,1.6) Lower risk with gown OR undef
(P=.006) Lower with masks OR 0.08 (.02,.33)
Loeb et al. ICAAC 2003: Cohort (43 nurses, 8 infected) Lower risk with gloves OR 0.45 (.44,
4.5) Lower risk with gown OR 0.36 (.10,1.2) Lower risk with masks OR 0.23 (.07,.78)
Number of SARs hospitalization days Mount Sinai Hospital
0
2
4
6
8
10
12
14
16
18
Num
ber
of c
ases
338 days of protected exposure(?1 staff infected)
MarchAprilMarch
31 hours of unprotected exposure(7 staff infected)
Transmission in the setting of any precautions, Toronto
Phase I - 260 patients 22 HCW infected intubation, cardiac arrest, “pre-intubation”
care
Phase II – 129 patients 3 HCW infected cardiac arrest, bronchoscopy, “pre-
intubation” care
Differences between Phase I and Phase II
HCW training and awareness “Enhancements”
Double gloves, hair & foot covering, greens
Practice issues Minimize time in room Minimize contact with patient Medical therapy to reduce cough/vomiting Minimize procedures that increase risk of
droplets
Protective Barriers: N95 masks, face shields, gown and gloves
Phase II
What went wrong?
NYGH-4W- June 6
0
1
2
3
4
5
6
7
4PT
4WHCWRelaxation of precautions
Impact on NYGH
HCWs 39 Patients 30 Visitors 18
Conclusions
Disease driven by exposure Transmission
Primarily in health care settings Droplet/contact Heterogeneous between patients
Control Unrecognized patients are the most
important problem Precautions include not only barriers, but
also practice Compliance with precautions is critical
Acknowledgements
Allison McGeer and Karen GreenThe staff and patients of greater Toronto area hospitals and public health departments
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