What is the history of the H5N1 virus?
The strain of avian flu most likely to cause a global pandemic among humans is the H5N1 subtype which was first detected in 1961 in terns living wild in South Africa. In 1997 the first transmission from birds to humans was reported during an outbreak of avian flu in Hong Kong. Eighteen people suffered respiratory infections and six died. The outbreak seemed to be controlled but it re-emerged in south-east Asia in late 2003 and early 2004 when 100 million birds were culled. In early 2004 there were 12 confirmed cases of H5N1 in Thailand and 23 in Vietnam, resulting in 23 deaths. Again the virus seemed to come under control but in late June 2004 it re-emerged again in several Asian countries, notably Cambodia, China, Indonesia and Malaysia as well as Thailand and Vietnam. To date there have been more than 100 cases in humans and about 60 deaths. The virus has now spread to birds in central Asia, Japan and Russia.
