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Occupational Health Conference
Muscat, 11-13 Dec 2006
Emerging Infections and
Health Care Workers
Professor David Koh
MBBS, MSc, PhD, FFOM, FFOMI, FFPH, FAMS
Department of Community, Occupational and Family Medicine
Faculty of Medicine
Emerging and Re-emerging Infectious Diseases, 1996 - 2001
SARS 20022003
Source: WHO, 2003
SARS
Probable cases of SARS worldwide, 7 August 2003. Source: WHO
Cumulative Total : 8,422 cases and 916 deaths, reported from 29 countries
SARS – an occupational health threat
• 20 % of SARS patients were HCWs (n=1706)
Range: 19% in the China, 43% in Canada
57% in Vietnam
• Differential risk for different types of HCWs
• All HCWs (including traditional healers)
are potentially at risk
• Even apparently low exposure
situations can pose a risk
D Koh, Lim MK, Chia SE.
SARS: health care work can be hazardous to health.
Occupational Medicine, 2003; 53 (4): 241-3.
Attack Rate for Health Care Workers in the
Hanoi French Hospital
Overall Attack Rate – 18%
Doctor – 16%
Nurse – 35%
Administrative staff – 2%
Other staff with patient contact – 53%
Patients admitted for other reasons - 7%
Source: WHO, 17 Oct 2003
Attack Rates among HCWs in Hong Kong
339 SARS infected HCWs in 14 of 16 Hospital Authority hospitals
that managed SARS cases (0% - 3.6, 4.4 %)
Staff Category
Attack Rate
Range
Nurses
1.21 %
0 – 4.7 %
Medical / Technical
0.29 %
0 – 1.5 %
* Non-medical support
2.73 %
0 – 13.3 %
Overall
1.2 %
* Healthcare assistants, cleaners, clerical staff
Lau JTF, Yang X, Leung P-C, Chan L, Wong E, Fong C, et al. SARS in three categories of
hospital workers, Hong Kong. Emerg Infect Dis [serial on the Internet]. 2004 Aug [date cited].
Available from: http://www.cdc.gov/ncidod/EID/vol10no8/04-0041.htm
High risk procedures
- Intubation, suction
- Nebulized aerosol therapy
- Positive pressure non-invasive
ventilation
The Inanimate Environment Can Facilitate Transmission
X represents VRE culture positive sites
~ Contaminated surfaces increase cross-transmission ~
Abstract: The Risk of Hand and Glove Contamination after Contact with a
VRE (+) Patient Environment. Hayden M, ICAAC, 2001, Chicago, IL.
Proximity is Important
Attack Rate of Medical Students, Prince of Wales Hospital
100% - for those who visited patients in beds
adjacent to an index case ( 3 / 3 )
50% - for those who entered the same cubicle
as an index case ( 4 / 8 )
0% - for those who had only entered the
same ward ( 0 / 8 )
Wong T-W, Lee C-K, Tam W, Lau JT-F, Yu T-S,
Lui S-F, et al. Cluster of SARS among
medical students exposed to single patient,
Hong Kong. Emerg Infect Dis [serial online]
2004 Feb [date cited]. Available from: URL:
http://www.cdc.gov/ncidod/EID/vol10no2/030452.htm
The impact of SARS extends
beyond the infection
* Psychological effects
High degree of distress experienced by
29 % - 35 % of hospital workers
* Overwork and job demands
* Social effects
* Effects on the family
Maunder R. The experience of the 2003 SARS
outbreak as a traumatic stress among frontline
healthcare workers in Toronto: lessons learnt.
Phil Trans R Soc Lond 2004
Study of SARS among HCWs in Singapore
Objectives
To study :
- work and non-work related problems
among health care workers in Singapore
Study Design
Questionnaire survey of
15,025 health care workers
in 9 health care settings,
from May-July 2003
D Koh, C Fones, MK Lim, SE Chia, F Qian, V Ng, S Emmanuel, NP Fong, G Koh, CT Kwa, BH Tan,
KS Wong, W Ng, Z Muttakin, KB Tan, WM Chew, HK Tang, SM Ko. Impact of SARS on Health
Care Workers in Singapore. Medical Care 2005 Jul;43(7):676-82.
Impact on Family and Social life
82% were concerned about
passing SARS to family
close friends,
colleagues
87% agreed that “people close
are worried for my health”
69% felt that “people close to
worried they might get
me”
members,
or work
to me
me are
infected through
Impact on Family and Social life
Negative
49% thought that “People
because of my job”
31% felt that “people avoid my
members because of my job”
avoid me
family
Positive
82% of respondents felt
the
hospital
employer”
77% felt “appreciated by society”
“appreciated by
/ clinic / my
SARS – a newly emergent
occupational disease
* Health care workers
* Animal and food
handlers
* Transport workers
flight attendants,
taxi drivers
preparation
-
* Laboratory Researchers
D Koh, Lim M-K, Ong C-N, Chia S-E. Occupational health response to SARS. Emerg
Infect Dis [serial on the Internet]. 2005 Jan [date cited]. Available from
http://www.cdc.gov/ncidod/EID/vol11no01/04-0637.htm
Will SARS Re-emerge ?
Most likely scenarios :
1 Original or new
animal reservoir
2 Undetected transmission
in humans (? Seasonal)
3 Persistent infection in humans
4 Laboratory accidents
Post July 2003 cases of SARS
Lab Accident # 1 - Singapore Sep 2003
27 year old postdoctoral student
23 Aug – 30 minutes at lab working on West Nile virus
26 August – Developed fever at midnight, later tested SARS +ve
Lab Accident # 2 - Taiwan Dec 2003
44 year old military researcher, at the Institute of Preventive Medicine
of the National Defense Medical Centre
# 1. Lim PL et al.
Laboratory-acquired severe acute respiratory syndrome.
N Engl J Med. 2004 Apr 22;350(17):1740-5.
# 2. Normile D.
accident fuels fears about SARS.
303: 26.
Second Lab
Science 2004. Jan 2004,
Guangdong, China
Dec
2003 – Jan 2004
1
32 y/o male TV producer
in apartment)
2
20 y/o restaurant waitress
3, 4
35 y/o businessman,
40 y/o hospital medical
director/physician
(rats
Diners
at restaurants (next door to, and at the restaurant where #2 worked)
FANG Ling et al. A serologic diagnosis and study on SARS antibody of newly occurred 4 confirmed SARS
cases in 2003-2004 in Guangdong, PR China. International Conference on SARS One Year After the (first)
Outbreak Musik- und Kongresshalle – Lübeck, Germany, May 8-11, 2004.
Liang G, Chen Q, Xu J, Liu Y, Lim W, Peiris JSM, et al. Laboratory diagnosis of four recent, sporadic cases of
community-acquired SARS, Guangdong Province, China. Emerg Infect Dis [serial on the Internet]. 2004 Oct
[date cited]. Available from http://www.cdc.gov/ncidod/EID/vol10no10/04-0445.htm
Beijing, April 2004
* 2 laboratory workers at the CDC’s
Institute of Virus Diseases
* Health care worker
* Family contacts
9 cases in all
1 death
Normile D. Severe acute respiratory syndrome: lab accidents prompt calls for new
containment program. Science. 2004 May 28;304(5675):1223-5.
Singaporean and Japanese
Health Care Worker
Perceptions, 2003
Are We Prepared ?
Singapore
n = 10,511
% felt "At great risk of exposure
SARS"
66%
Japan
n = 7,282
to
64%
% “Afraid of falling ill with SARS"
76%
55%
% felt that "Protective measures
were effective"
96 %
31%
% thought that "Protective measures
were necessary and important"
95 %
88%
% felt that “Policies and protocols
clear”
93%
were
65%
% thought that “Policies and
implemented"
90 %
50%
% felt that “Recommended measures
were adhered to"
92 %
protocols were
43%
Learning Point
Initial infections of HCWs at the outset of an
outbreak may sometimes be due to perceptions that
recommended
policies
and
measures
are
unnecessary or excessive.
…. efforts to educate and communicate the rationale
and importance of protective measures may be
especially important when outbreaks seem distant
and perceived danger is low.
D Koh, K Takahashi, MK Lim, T Imai, SE Chia, F Qian, V Ng, C Fones. SARS
risk perception and preventive measures, Singapore and Japan. Emerg Infect
Dis [serial on the Internet]. 2005 Apr [date cited]. Available from
http://www.cdc.gov/ncidod/EID/vol11no04/04-0765.htm
H1
N1
H2
N2
H3
N3
H4
N4
H5
N5
H6
N6
H7
N7
H8
N8
H9
N9
H10
H11
H12
H13
H14
H15
Influenza A Viruses
Orthomyxovirus - with
segmented ssRNA genome
8
Subtypes based on basis of two
surface antigens:
- Hemagglutinin (H)
- Neuraminidase (N)
H1N1, H3N2 and H1N2 affect
humans and are globally
circulated
H5N1 - causes avian influenza
Source:
Nicholson, Wood and Zambon.
Lancet 2003; 362: 1733-45.
Why the Concern about H5N1
H5N1 strain mutates frequently
H5N1 has the capacity to jump the
barrier to cause disease in
(documented in 1997, 2003, 04, 05)
species
humans
H5N1 infection in humans has a high fatality rate
Linda Stannard, of the Dept of Medical
Microbiology, University of Cape Town
Genetic mutation in the last few years show increasing H5N1
virulence and capacity to infect mammals
? Emergence of a new subtype of virus that can infect
humans and be transmitted to other humans
Hong Kong, SAR 1997
18 Human cases of H5 N1 influenza
9 were children < 10 yrs
7 mild disease
11 severe with pneumonia
6 fatalities (< 10 yrs, 1/9 ; > 12 yrs 5/9)
* Close contacts with affected poultry
Index case had contact with chickens and ducks in school
3 cases purchased poultry from market before illness
2 cases had live H5N1+ve chicken outlet near their home
5 cases had regular visits to markets/live chicken outlets
1 case worked in the market
Tam JS. Influenza A (H5N1) in Hong Kong: an overview. Vaccine 20 (2002): S77-S81.
29 Dec 1997 – 15 Jan 1998
Serological survey of 293 government
workers (cullers) and 1525 poultry workers
Poultry Workers
10 % sero+ve for H5 (by microneutralization
Western blot assay)
and
Risk factors: butchering poultry, exposure
poultry with >10% mortality
to
Government Workers (Cullers)
3% were sero+ve for H5
229 (78%) had paired serum samples (2 wks later)
1 seroconverted (respiratory illness on 27 Dec)
Bridges CB et al. Risk of Influenza A (H5N1) infection among poultry workers, Hong
Kong, 1997-1998. J Infect Dis 2002; 185: 1005-10.
H5N1 Transmission to Health Care Workers
217 exposed, 309 non-exposed HCWs studied
Exposed and non-exposed HCWs
difference in poultry exposure
reported no
89% of exposed HCWs had paired serum samples
3.7% (8/217) of exposed HCWs were H5N1 sero+ve
these exposed HCWs seroconverted)
(2 of
0.7% (2/309) of non-exposed HCWs were H5N1 sero+ve
Risk factors:
patient, changing bed linen of patient
Bathing
From: BBC
Bridges CB et al. Risk of influenza A (H5N1) infection among health care workers exposed to
patients with influenza A (H5N1), Hong Kong. J Infect Dis 2000; 181:344-8.
As at 29 Nov – 258 cases, 154 deaths
http://gamapserver.who.int/mapLibrary/Files/Maps/Global_H5N1inHumanCUMULATIVE_FIMS_20061113(2).png
H5N1 in Other Animals
Haiyan L. I. & Chin J.
Chinese J. Prev. Vet. Med., 26. 1 - 6 (Jan 2004)
H5N1 virus found in 2003 in pigs in southeast China
Haiyan L. I. & Chin J.
Chinese J. Prev. Vet. Med., 24. 304 - 309 (May 2004)
Reported similar results from pigs tested elsewhere
in 2001 and 2003
H5N1 in CATS
– leopards, tigers, domestic cats
http://www.fao.org/ag/againfo/subjects/en/health/diseases-cards/avian_cats.html
Report of probable person to person
transmission of bird flu in Thailand
Patient
Mother
Index patient (Sep 2004)
- 11 year old girl, who became ill a few
days after exposure to dying chickens
Mother (no history or poultry exposure)
- travelled from distant city to provide
16-18 hours of unprotected nursing care
Mother died from pneumonia – autopsy tissue +ve for H5N1
Aunt also provided unprotected nursing, and developed fever and
pneumonia
Nasopharyngeal & throat swabs +ve for H5N1
K. Ungchusak et al. Probable person-to-person
transmission of avian influenza A (H5N1).
New Engl. J. Med, 2005: 352 333–340. 27 Jan 2005
Aunt
SCIENCE Vol 308 No 5721 22 April 2005
Update on North Vietnam
- 70 % mortality previously
- 20 % mortality since Jan 2005
- Cases occur in larger clusters
members in one family
e.g. 5
- Previously among children, young adults, but now
people of all ages
affects
- Disease appears to be less virulent and more infectious
- Still ? no evidence of person-person transmission
Influenza Pandemics in the Last Century
1918-19
Spanish Influenza
H1 N1
30 million deaths
H2 N2
1 million deaths
H3 N2
800,000 deaths
39 years later . . .
1957-58
Asian Influenza
11 years later . . .
1968-69
Hong Kong Influenza
38 years later . . .
winter
2006 ? ? ?
Summary
Several viral zoonotic diseases have
recently emerged
Occupational exposures are
relevant in many cases
Healthcare workers are at risk
Illnesses are severe with
mortality rates of 10%-75%
These outbreaks recur - we
should be alert & prepared