Proliferation of bird flu outbreaks raises risk of human pandemic.

The global spread of bird flu and the number of viral strains currently circulating and causing infections have reached unprecedented levels, raising the risk of a potential human outbreak, according to disease experts. Multiple outbreaks have been reported in poultry farms and wild flocks across Europe, Africa and Asia in the past three months. While most involve strains that are currently low risk for human health, the sheer number of different types, and their presence in so many parts of the world at the same time, increases the risk of viruses mixing and mutating - and possibly jumping to people. "This is a fundamental change in the natural history of influenza viruses," Michael Osterholm, an infectious disease specialist at University of Minnesota, said of the proliferation of bird flu in terms of geography and strains - a situation he described as "unprecedented". Global health officials are worried another strain could make a jump into humans, like H5N1 did in the late 1990s. It has since caused hundreds of human infections and deaths, but has not acquired the ability to transmit easily from person to person. The greatest fear is that a deadly strain of avian flu could then mutate into a pandemic form that can be passed easily between people - something that has not yet been seen. While avian flu has been a prominent public health issue since the 1990s, ongoing outbreaks have never been so widely spread around the world - something infectious disease experts put down to greater resilience of strains currently circulating, rather than improved detection or reporting. While there would normally be around two or three bird flu strains recorded in birds at any one time, now there are at least half a dozen, including H5N1, H5N2, H5N8 and H7N8. The Organization for Animal Health (OIE) says the concurrent outbreaks in birds in recent months are "a global public health concern", and the World Health Organization's director-general warned this week the world "cannot afford to miss the early signals" of a possible human flu pandemic. continue