The Bird Flu Threat - Why Aren't We Worrying? - Malaysian Abstracting and Indexing System

Fauziah Mohamad Idris, (2005) The Bird Flu Threat - Why Aren't We Worrying? Malaysian Journal of Medical Sciences, 12 (1). ISSN 1394195X

Abstract

H5N1 is now widely entrenched in Asia and this signals that the world has moved closer to the next pandemic. Poultry husbandry in much of East Asia generally pays scant regard to hygiene practices and the movement of infected poultry, either by design or accident, is thought to have played a part in spreading the disease. Domestic and international trade in wild birds for both food and caged pets,involves millions of individuals annually and the frequent occurrence of mixed markets could allow viruses to pass between species and cross borders.
The hiding of fighting cocks to avoid slaughter in Thailand may also have contributed to the spread, or at least hampered eradication. The role of migratory birds in the movement of H5N1 could not be discounted but it is noteworthy that surveillance of wild birds has resulted in very few isolations of H5N1 during either the current or previous Asian outbreaks. Prior to 1997, avian influenza was confined to animals with no direct spread to humans.
However in 1997, 18 human cases of avian influenza with 6 deaths were reported in Hong Kong. Coinciding with outbreaks of highly pathogenic H5N1 in poultry. In 2003, two other avian influenza viruses, A/H7N7 and A/H9N2, had also caused human illnesses in the Netherlands and Hong Kong respectively. Since time immemorial, influenza A virus had been evolving with the production of totally different subtypes every 10 to 15 years. The evolution is
largely due to its unique segmented genome that allows for easy recombination of its genetic materials when two different strains of influenza viruses infect a cell. Environmental factors provide selective pressure in producing mutant viruses and it was postulated that the current A/H5N1 virus could have resulted following widespread vaccination of poultry with H5 vaccine in mainland China, as a preventive response to the 1997 Hong Kong’s avian influenza outbreak. The role of influenza vaccine in the prevention of avian influenza in poultry is
controversial, at best. Despite vaccination, sub clinical infections could still be occurring and these would not be detected if post-vaccination surveillance were not put in place. The scenario allows the virus to circulate longer than usual in the avian host population with the risk of viral mutations highly likely to occur. Animals are almost always involved in production of new influenza viruses and
in each of the three pandemics – the 1918 “Spanish flu”, the “Asian flu” of 1957, and the “Hong Kong flu” of 1968 – the viruses originated in Asia, most likely somewhere in China. Since January 2004, the outbreaks of H5N1 avian influenza in Asia had caused 50 deaths in 80 confirmed human cases, with cases reported only from Vietnam, Thailand and Cambodia. The H5N1 virus had already caused limited human-to-human transmission and it is only a matter of time before the virus adapt more efficient human transmission method.

The Bird Flu Threat - Why Aren't We Worrying?

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Abstract