Bird Flu Virus in Poultry Resurfaces
Threat of a Human Pandemic Reappears in December 2008
Jan 5, 2009
After a two-year decline in the number of confirmed human deaths from H5N1 bird flu, there are recent reports that India, Bangladesh, Vietnam and mainland China had experienced outbreaks in December 2008. It may mean that the threat of a human pandemic from the virus is not over.
History of the Bird Flu Virus
Scientific literature describes a number of H5N1 flu viruses circulating in southeastern China since 1996. Since 2001, although these viruses have been closely related, there has been a sharp increase in their genetic diversity from the major protein found on the virus in 1997. In Hong Kong that virus appeared to jump from chickens to humans, infecting 18 people and killing six of them, and was different than the one discovered in 2003. The explosion in variation coincides with the period during which Chinese farmers practiced widespread vaccinations of chickens against the flu. In 2003 scientists developed an improved flu vaccine for poultry; however they are now concerned that the vaccines could mask disease signs while the birds continue to shed viruses. (New Scientist, 02/11/2004)
Economic Effects of Bird Flu
It has been estimated that as many a half a billion fowl have been killed by the virus or culled to contain its spread. This has caused enormous economic strain and food shortages in the countries affected by it. When it was discovered in Hong Kong in 1997, Hong Kong ordered its entire poultry population, estimated at 1.6 million birds, destroyed in three days.
New Cases of Bird Flu
New cases have appeared after a two-year decline in the number of confirmed human deaths from H5N1 bird flu. Fewer countries had been reporting outbreaks among poultry. The United Nations had released information in October 2008, crediting improved surveillance and the rapid culling of potentially infected poultry to help contain and even prevent outbreaks in many countries. However, Michael T. Osterholm, director of the Center for Infectious Diseases Research and Policy at the University of Minnesota in Minneapolis, thinks that the virus has continued, smoldering and then flaring up again. Many human cases were traced to direct contact with poultry, especially in Southeast Asia where many people have backyard flocks and few wear gloves while handling them.
Hong Kong Outbreak 2008
The Chinese government thought it had stamped out H5N1 in its territories, such as Hong Kong, after the outbreak in 2003. Since then it had vaccinated poultry against the virus and strictly regulated farm sanitation. In the latest outbreak at two large farms, it killed 60 chickens that might have been infected. They began looking for the source of the infection and testing the effectiveness of the vaccine used since 2003, inoculating chickens, geese and ducks against the virus. It is believed that the H5N1 virus may have mutated to break through the vaccine as often happens, including those used for humans. (Los Angeles Times, 12/04/2008)
This recent outbreak of bird flu has reinforced health warnings about the way H5N1 can mutate and that it will require scientists to continue developing new vaccines if the infection is to be contained.
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