Professor David Koh

MBBS, MSc, PhD, FFOM, FFOMI, FFPH, FAMS

Department of Community, Occupational and Family Medicine

Faculty of Medicine

Occupational Health ConferenceMuscat, 11-13 Dec 2006

Emerging Infections and Health Care Workers

Source: WHO, 2003

Emerging and Re-emerging Infectious Diseases, 1996 - 2001

SARS 2002-2003

Probable cases of SARS worldwide, 7 August 2003. Source: WHOCumulative Total : 8,422 cases and 916 deaths, reported from 29 countries

SARS

• 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

SARS – an occupational health threat

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 %

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

* Healthcare assistants, cleaners, clerical staff

High risk procedures

- Intubation, suction

- Nebulized aerosol therapy

- Positive pressure non-invasive ventilation

The Inanimate Environment Can Facilitate Transmission

~ 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.

X represents VRE culture positive sites

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/vol10no2/03-0452.htm

The impact of SARS extends beyond the infection

* Psychological effectsHigh degree of distress experienced by 29 % - 35 % of hospital workers

* Overwork and job demands

* Social effects

* Effects on the familyMaunder 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 DesignQuestionnaire 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 aboutpassing SARS to family members, close friends, or work colleagues

87% agreed that “people close to me are worried for my health”

69% felt that “people close to me are worried they might get infected through me”

Impact on Family and Social life

Negative

49% thought that “People avoid me because of my job”

31% felt that “people avoid my family members because of my job”

Positive

82% of respondents felt “appreciated by the hospital / clinic / my employer”

77% felt “appreciated by society”

SARS – a newly emergent occupational disease

* Health care workers

* Animal and food preparation handlers

* Transport workers - flight attendants, taxi drivers

* Laboratory ResearchersD 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

Most likely scenarios :

1 Original or new animal reservoir

2 Undetected transmission in humans (? Seasonal)

3 Persistent infection in humans

4 Laboratory accidents

Will SARS Re-emerge ?

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. Second Lab accident fuels fears about SARS. Science 2004. Jan 2004, 303: 26.

1 32 y/o male TV producer (rats in apartment)

2 20 y/o restaurant waitress

3, 4 35 y/o businessman, 40 y/o hospital medical director/physician

Diners at restaurants (next door to, and at the restaurant where #2 worked)

Guangdong, China Dec 2003 – Jan 2004

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 deathNormile D. Severe acute respiratory syndrome: lab accidents prompt calls for new containment program. Science. 2004 May 28;304(5675):1223-5.

Singapore Japann = 10,511 n = 7,282

% felt "At great risk of exposure to SARS" 66% 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 were clear” 93% 65%

% thought that “Policies and protocols were implemented" 90 % 50%

% felt that “Recommended measures were adhered to" 92 % 43%

Singaporean and Japanese Health Care Worker Perceptions, 2003

Are We Prepared ?

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

Learning Point

Influenza A Viruses

Source: Nicholson, Wood and Zambon. Lancet 2003; 362: 1733-45.

H1

H2

H3

H4

H5

H6

H7

H8

H9

H10

H11

H12

H13

H14

H15

N1

N2

N3

N4

N5

N6

N7

N8

N9

Orthomyxovirus - with 8 segmented ssRNA genome

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

Why the Concern about H5N1

H5N1 strain mutates frequently

H5N1 has the capacity to jump the species barrier to cause disease in humans (documented in 1997, 2003, 04, 05)

H5N1 infection in humans has a high fatality rate

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

Linda Stannard, of the Dept of Medical Microbiology, University of Cape Town

Hong Kong, SAR 199718 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.

Bridges CB et al. Risk of Influenza A (H5N1) infection among poultry workers, Hong Kong, 1997-1998. J Infect Dis 2002; 185: 1005-10.

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 and Western blot assay)

Risk factors: butchering poultry, exposure to poultry with >10% mortality

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 health care workers exposed to patients with influenza A (H5N1), Hong Kong. J Infect Dis 2000; 181:344-8.

217 exposed, 309 non-exposed HCWs studied

Exposed and non-exposed HCWs reported no difference in poultry exposure

89% of exposed HCWs had paired serum samples

3.7% (8/217) of exposed HCWs were H5N1 sero+ve (2 of these exposed HCWs seroconverted)

0.7% (2/309) of non-exposed HCWs were H5N1 sero+ve

Risk factors: Bathing patient, changing bed linen of patient

H5N1 Transmission to Health Care Workers

From: BBC

http://gamapserver.who.int/mapLibrary/Files/Maps/Global_H5N1inHumanCUMULATIVE_FIMS_20061113(2).png

As at 29 Nov – 258 cases, 154 deaths

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 Other Animals

http://www.fao.org/ag/againfo/subjects/en/health/diseases-cards/avian_cats.html

H5N1 in CATS

– leopards, tigers, domestic cats

Report of probable person to person transmission of bird flu in Thailand

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 careMother died from pneumonia – autopsy tissue +ve for H5N1

Aunt also provided unprotected nursing, and developed fever and pneumoniaNasopharyngeal & 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

Patient Mother 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 e.g. 5 members in one family

- Previously among children, young adults, but now affects people of all ages

- 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

39 years later . . .

1957-58 Asian Influenza H2 N2 1 million deaths

11 years later . . .

1968-69 Hong Kong Influenza H3 N2 800,000 deaths

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 - weshould be alert & prepared