Although Hong Kong "bird flu" killed six people - the latest yesterday is dead - and prompted the slaughter of 1.5 million chickens, it remains largely a mystery to scientists. Now a team of US and Hong Kong has yet taken the most detailed look at the genes of the virus. Although scientists can not yet explain the jump of the virus from birds to humans, the partial sequence, reported in tomorrow's issue of Science , provides a clue to why the virus can be a such an effective killer.
This particular virus was isolated from a 3 year old boy in Hong Kong, who died in May after coming down with a flu-like illness that does not match any known strains human influenza ( science , 12 September, p. 10). It did, however, is an avian strain named H5N1 due varieties of hemagglutinin and neuraminidase on its surface. The discovery has triggered public health alarm. Because there was no trace of the avian strain infecting people, no immunity to it, and epidemiologists feared it could trigger a pandemic
By analyzing the DNA sequence virus, researchers led by Kanta Subbarao of the Centers for Disease Control and Prevention in Atlanta have discovered what could be a clue to the deadliness of the strain. When they have sequenced the hemagglutinin gene, they found an insertion side to a central place where cellular enzymes breaking using the host except for the virus coat protein, which allows the virus to infect cells. In birds, enzymes that cleave the protein are more concentrated in the digestive and respiratory systems, so that most strains of flu can infect cells, said team member Michael Perdue of the US Department of Laboratory poultry research Southeast of Agriculture in Athens, Georgia. But the insert can provide easier - target for the enzymes, allowing the virus to infect the heart vessels, brain, and blood - and less specific. It is not known if the virus works the same way in humans, however.
In fact, scientists still do not know exactly how this strain of flu manages to infect humans at all. To resolve this issue, Subbarao said the researchers closely examine a range of avian flu, hoping to identify how this strain H5N1 is different. However, the virus has changed to allow the bird to human infection, it does not pass easily between humans. So far, there has only been one suspected case of transfer from one person to another.
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