Avian Influenza | Bird Flu

Current Status of H5N1 in Asia and Europe

Avian influenza caused by H5N1 in Asia was initially recognized in Hong Kong in 1997. During that outbreak, 18 human cases were recognized; six patients died. The outbreak was stopped when all of the domestic chickens present in wholesale facilities and vendors in Hong Kong were slaughtered (see References: Snacken 1999). Person-to-person transmission of H5N1 was not recognized (see References: Uyeki 2002).

H5N1 avian influenza resurfaced in December 2003 initially in South Korea, with additional outbreaks reported in January 2004 in Vietnam, Japan, Thailand, Cambodia, and China. The first wave lasted through March 2004. A second wave occurred in July and August 2004, and a third began in December 2004 and continues, having reached Europe very recently. To date, the following countries have reported outbreaks of H5N1 avian influenza:

Cambodia, China, Hong Kong, Indonesia, Japan, Laos, Malaysia, South Korea, Thailand, Vietnam, Russia, Kazakhstan
Mongolia, Turkey, Romania, Croatia

The unprecedented rapid spread of H5N1 avian influenza across East Asia and now reaching Europe has been alarming to international health organizations, and efforts to contain its spread are ongoing. Control measures currently recommended in Asia are outlined in the sections below on Prevention and Outbreak Control in Poultry.

Despite extensive control efforts, during the fall of 2004 new outbreaks of H5N1 avian influenza continued to be reported in Cambodia, Hong Kong, Indonesia, Malaysia, and Thailand. On June 8, 2005, China reported that several hundred migratory geese and other wild birds had died of H5N1 in the northwestern part of the country (see References: OIE: Highly pathogenic avian influenza in the People's Republic of China – May 2005). In late summer 2005, reports of H5N1 in Russia, Kazakhstan, and Mongolia began appearing; the H5N1 in those areas is being studied to determine whether and how it is related to the strain in Southeast Asia. In October 2005 H5N1 was reported in birds in Turkey, Romania, and Croatia.

A report from the Food and Agricultural Organization of the United Nations (FAO) published in September 2004 indicates that H5 avian influenza viruses have become endemic in parts of Southeast Asia and that existing reservoirs in ducks, wild birds, and potentially pigs "pose a serious challenge to eradication"Other alarming features of H5N1 include the following.

Studies comparing virus samples over time indicate that the virus has become progressively more pathogenic for poultry.
The current strain of the virus is now able to survive several days longer in the environment compared with when it first emerged.

The virus appears to be expanding its mammalian host range, as indicated in the section above on "Hosts."

The virus has been found increasingly in dead migratory birds (which are usually not clinically affected by HPAI viruses); this supports the growing virulence of the current virus.

An international conference sponsored by the World Health Organization (WHO) and OIE and held in Ho Chi Minh City in February 2005 concluded that the agricultural losses from the current H5N1 avian influenza outbreak as of February 2005 are estimated at $10 billion. Conference participants also noted that about $100 million is needed in the region to strengthen animal health and laboratory diagnostic services.

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1. Definition of Avian Influenza?

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5. Key Outbreaks of HPAI in Domestic Avian Populations?

6. Current Status of H5N1 in Asia?

7. HPAI As a Biological Weapon?

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