Presentation on theme: "1 The Environment and Emerging Biological Hazards In The Pacific Basin David Koh MBBS (S’pore), MSc (Occup Med), PhD (Birm), FFOM (Lond), FFOM (Ire), FFPH."— Presentation transcript:
1 The Environment and Emerging Biological Hazards In The Pacific Basin David Koh MBBS (S’pore), 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 Seminar on Public Health & The Environment In the Pacific Basin Singapore – Auckland, 22 Apr 2006
2 Emerging Infectious Diseases Definition Diseases in flux, either rising in incidence, expanding in host or geographic range, or changing in pathogenicity, virulence, or some other factor
3 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
4 Source: WHO, 2003 SARS 2002-2003 Emerging and re-emerging biological hazards in the world ?
5 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; 268:947. 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.
6 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 2000;288(5470):1432-5.
7 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; 27;342(17):1229-35.
8 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. Nipah’s return. Scientific American 2004 Sep;291(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.htm
9 Probable cases of SARS worldwide, 7 August 2003. Source: WHO Cumulative Total : 8,422 cases and 916 deaths, reported from 29 countries SARS
10 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
11 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
12 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 ? 4 cases in China, Dec 03-Jan 04
13 Influenza A Viruses Source: Nicholson, Wood and Zambon. Lancet 2003; 362: 1733-45. 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
14 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
15 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
16 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
18 Influenza Pandemics in the Last Century 1918-19 Spanish Influenza H1 N130 million deaths 39 years later... 1957-58 Asian Influenza H2 N21 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
19 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