THE bird flu virus spreading through Turkey could be accumulating mutations that are helping it adapt to humans. But fears of an imminent pandemic may be premature, as the virus is showing none of the mutations鈥� feared effects.
Samples of the H5N1 virus that killed Turkish teenagers Fatma and Mehmet Ali Kocyigit early this month have now been sequenced at the National Institute for Medical Research in London. Some of Mehmet鈥檚 virus had a mutation in a surface protein called haemagglutinin, which makes it better at binding to cells in the human respiratory tract as well as to cells in birds.
While this is worrying, it is not clear whether that mutation alone is enough to make the virus any better at spreading among humans than before. 鈥淲e鈥檒l know it means something if we see it in a cluster of human cases,鈥� says Michael Perdue of the World Health Organization. A cluster could mean the mutation is being selected for by being transmitted from human to human.
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鈥淭he mutation makes it better at binding to cells in the human respiratory tract鈥�
Mehmet鈥檚 virus also carried a mutation in the polymerase gene that has been shown to make it more lethal to mice. But if anything the cases in Turkey have been milder than those elsewhere.
What now seems undeniable is that wild birds spread H5N1 from central Asia to Turkey. The virus taken from the teenagers is most closely related to a distinctive strain that was found in wild geese and ducks at Qinghai Lake in China in the spring of 2005 and has since crossed Russia and circled the Black Sea.
