The Environment and Emerging Biological Hazards In The Pacific Basin

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Seminar on Public Health The Environment In the
Pacific Basin Singapore Auckland, 22 Apr 2006
The Environment and Emerging Biological Hazards
In The Pacific Basin David Koh MBBS (Spore),
MSc (Occup Med), PhD (Birm), FFOM (Lond), FFOM
(Ire), FFPH (UK), FAMS Professor and
Head Department of Community, Occupational
and Family Medicine Yong Loo Lin School
of Medicine
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Emerging Infectious Diseases Definition Diseas
es in flux, either rising in incidence, expanding
in host or geographic range, or changing in
pathogenicity, virulence, or some other factor
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• Why do these diseases emerge ?
• Emergence almost always driven by
• Large-scale environmental change
  e.g. deforestation, agricultural
  encroachment, urban sprawl
• Change in human population structure
• e.g. increased density linked to
  urbanization
• Change in human behavior
• e.g. increasing drug use, changes in
  medical practice, agricultural
  intensification, international trade

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Emerging and re-emerging biological hazards in
the world
?
SARS 2002-2003
Source WHO, 2003
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Hendra Virus Outbreaks (Australia) Hendra
Virus Family Paramyxoviridae Genus
Henipavirus (Nipah and Hendra viruses) 1994-95
Queensland outbreak (3 cases, 2 deaths) 1999
outbreak - close contact with infected
horses Clinical features of Hendra virus
infection severe flu-like symptoms, subsequent
encephalitis, respiratory and renal
failure Murray K, Selleck P, Hooper P. A
morbillivirus that caused fatal disease in horses
and humans. Science 1995 268947. Black, P., et
al.  2001.  Serological examination for evidence
of infection with Hendra and Nipah viruses in
Queensland piggeries.  Australian Veterinary
Journal.  June 79 (6) 424-426.
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Nipah Virus Family Paramyxoviridae Genus
Henipavirus (Nipah and Hendra
viruses) Enveloped, Single stranded,
non-segmented RNA genome Virus named after
village near Kuala Lumpur from where it was first
isolated Sep 1998- Apr 1999 - 265
cases, 105 died
Chua et al. Nipah virus a recently emergent
deadly paramyxovirus. Science 2000288(5470)1432-
5.
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• Nipah virus outbreaks (Malaysia/Singapore
  1998-1999)
• Sep 1998 Apr 1999
• Malaysia (265 cases, 105 died)
• Almost all had exposure to pigs
• Incubation 4 -18 days, May be mild / inapparent
  infection
• In symptomatic cases,
• influenza like symptoms with high fever,
  myalgia
• encephalitis, convulsions and coma (40
  mortality)
• Singapore (11 cases, 1 died)
• contact with infected pigs
• Goh et al. Clinical features of Nipah virus
  encephalitis among pig farmers in Malaysia. N
  Engl J Med 2000 27342(17)1229-35.

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Re-emergence in Bangladesh (2004) Apr-May 2001,
Jan 2003 outbreaks in Bangladesh mainly
children 74 mortality Jan- Apr 2004 outbreak -
killed 35 people - children who had
direct contact with bat-contaminated fruit
Choi C. Nipahs return. Scientific American
2004 Sep291(3)21A, 22. Hsu VP, Hossain
MJ, Parashar UD, Ali MM, Ksiazek TG, Kuzmin I, et
al. Nipah virus encephalitis reemergence,
Bangladesh. Emerg Infect Dis serial on the
Internet. 2004 Dec date cited. Available from
http//www.cdc.gov/ncidod/EID/vol10no12/04-0701.ht
m
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SARS
Probable cases of SARS worldwide, 7 August 2003.
Source WHO
Cumulative Total 8,422 cases and 916 deaths,
reported from 29 countries
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Early cases of SARS
More than 1/3 of cases with dates of onset
before 1 Feb. 2003 were persons who handled,
killed or sold food animals, or those who
prepare or serve food
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SARS-CoV Animal and Environmental Reservoirs
Domestic animals
Cats, dogs ( ve in oropharyngeal and
rectal swabs) Others
Rodents
(rats) Wildlife
Masked palm civet cat
Racoon dog
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Will SARS Re-emerge ?

• Most likely scenarios
• Original or new animal reservoir
• Undetected transmission in humans (?
  Seasonal)
• Persistent infection in humans
• Laboratory accidents

4 cases in China, Dec 03-Jan 04
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Influenza A Viruses
Orthomyxovirus - with 8 segmented ssRNA
genome Subtypes based on basis of two surface
antigens - Hemagglutinin (H) (15) -
Neuraminidase (N) (9) H1N1, H3N2 and H1N2
affect humans and are globally circulated H5N1 -
causes avian influenza
Source Nicholson, Wood and Zambon. Lancet
2003 362 1733-45.
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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, 2003-06) 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
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Why Asia ? Densely packed people
living closely with birds / animals
Farming and marketing habits - ducks,
chickens, pigs kept together with family -
shopping at live animal markets Major bird
migratory pathways - from Siberia across Asia
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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/d
iseases-cards/avian_cats.html
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http//gamapserver.who.int/mapLibrary/app/searchRe
sults.aspx
Total 194 cases 109 deaths(56)
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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 37 years later . . .
2006 ? ? ? Bird flu or something
else ? ? ? millions

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Summary Several infectious diseases recently
emerged in the Pacific basin Emergence due to
changes in the environment / people Illnesses are
severe with mortality rates of 10-75 These
outbreaks recur we should be alert prepared A
worldwide pandemic may be imminent