The Threat of Pandemic Influenza Are We Ready? Workshop Summary (2005) / Chapter Skim
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From page 115... ...
. The past decade has seen increasingly frequent and severe outbreaks of highly pathogenic avian influenza, as described in the Summary and Assessment.
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From page 116... ...
. These findings indicate that domestic ducks in southern China played a central role in the generation and maintenance of H5N1 and that wild birds spread the virus across Asia, to the point where it is now endemic in the region -- an ecological niche from which it now presents a long-term pandemic threat to humans.
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From page 117... ...
. To trace the ecological and genetic origins of these outbreaks, we compared H5N1 viruses recently isolated from poultry in Indonesia, Thailand, and Vietnam as well as from humans in Thailand and Vietnam with 253 H5N1 isolates obtained during prospective surveillance of live poultry markets in Hong Kong and in Guangdong, Hunan, and Yunnan provinces, China, from 2000 to 2004 (Figure 2-1)
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From page 118... ...
The genes of the virus isolates that encode the surface antigens haemagglutinin (HA) and neuraminidase (NA)
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From page 119... ...
.12 The M and NS genes were closest to those of influenza viruses of diverse subtypes isolated from ducks in southern China, suggesting that aquatic avian viruses were the gene donors for these new reassortants (Figure 2-4b; see also Supplementary Fig.
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From page 120... ...
Number of Genotypes 2 6 Faecal droppings from apparently healthy poultry in live poultry markets in Hong Kong (200004) , Guangdong (200004)
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, a group of antiviral drugs used for treatment of human influenza. Sequence analysis revealed that Asp 31 was present in all avian and human genotype Z viruses isolated in Thailand and Vietnam, but in only one of six viruses isolated from poultry in Indonesia.
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From page 122... ...
Further reassortment of genotype E with other aquatic avian influenza viruses gave rise to the genotypes X0X3, distinguished by the sources of their PB2, PA, and NS genes. Genotype W differs from genotype B only in its PB2, NP, and M genes.
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From page 124... ...
Green text indicates viruses isolated from wild birds in Hong Kong; pink text indicates viruses from smuggled birds in China; and other colours show the country of origin of isolates from the late 2003 to early 2004 H5N1 outbreak. Underlined viruses have the amantadine-resistance mutation (Ser31Asn)
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From page 125... ...
The HA molecules of most genotype Z viruses isolated since late 2002 in Hong Kong, of two out of six isolates from Indonesia, and of all isolates from Thailand, Vietnam, and Yunnan Province in late 2003 and early 2004 had acquired a potential N-linked glycosylation site at positions 154156. Glycosylation at this site, adjacent to the receptor-binding (Claas et al., 1998)
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From page 126... ...
In Hong Kong between late 2002 and the time of this report, genotype Z+ H5N1 virus was isolated from a dead little egret (Egretta garzetta) , and genotype Z viruses were isolated from two dead grey herons (Ardea cinerea)
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From page 127... ...
. Methods Surveillance, Virus Isolation and Characterization Faecal droppings from apparently healthy poultry in live poultry markets in Hong Kong and in Guangdong, Hunan, and Yunnan provinces were sampled monthly for influenza virus isolation.
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From page 128... ...
The standard is also divided by nature of the house, size, and type of the farm. The standard is a guideline for poultry farmers to improve the biosecurity system on their farms to prevent avian influenza outbreak.
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From page 129... ...
Clinical surveillance will be applied at all times. To support the national surveillance program for AI, the DLD allocated funding to the National Institute of Animal Health, and all Regional Diagnostic Centers were mandated to improve their facilities and increase capacity.
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This section describes how poultry is raised in Vietnam, how the avian influenza outbreak occurred, and how the country tried to control the disease. It also discusses factors that influenced the effectiveness of AI control measures as applied in Vietnam.
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From page 131... ...
The more numerous meat ducks are kept in the rice fields to collect the fallen rice grains during the harvest seasons. Recently, with the introduction of supermeat ducks and Muscovy ducks from abroad, industrial duck raising has begun in some places.
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From page 132... ...
and aquatic birds (ducks and Muscovy ducks) , particularly adult animals, developed clinical disease and suffered high rates of both morbidity and mortality.
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From page 133... ...
Government Response The Vietnamese government issued several important and decisive directives and orders in response to the AI outbreak, including the following: · A Steering Committee led by the Director of the Department of Animal Health was established on January 10, 2004, as a result of the Prime Minister's telegram to the Chairmen of provinces (No. 71/CP-NN dated on January 8)
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From page 134... ...
These include: · The decisive determination of the Vietnamese government to extinguish the outbreak by applying lessons learned from efforts to control Severe Acute Respiratory Syndrome (SARS) in Vietnam in early 2003.
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From page 135... ...
H5N1 AI has been reported repeatedly in neighboring Hong Kong and in the nearby southern provinces of China, a region considered to be the epicenter of influenza. Logically, Vietnam should have been prepared to face influenza in general and AI in particular.
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From page 136... ...
However, because this process is time consuming, it would be better to put in place a system of early, on-the-spot detection and virus characterization. This would help Vietnamese authorities react in time to prevent farmers from selling infected birds, thereby limiting disease transmission.
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From page 137... ...
. Moreover, evidence indicates that all human influenza viruses are of avian origin.
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From page 138... ...
2002. Emergence of multiple genotypes of H5N1 avian influenza viruses in Hong Kong SAR.
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1999. The surface glycoproteins of H5 influenza viruses isolated from humans, chickens, and wild aquatic birds have distin guishable properties.
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From page 140... ...
2004. Reemerging H5N1 influenza viruses in Hong Kong in 2002 are highly pathogenic to ducks.
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