The latest instance of human-to-human transmission of H5N1 bird flu was confirmed in Indonesia on Friday.
Although seven people died in the cluster, Keiji Fukuda, coordinator of the World Health Organization鈥檚 global influenza programme, said the virus that killed them did not pose a great threat of wider transmission.
The virus had mutated, but not into a form that could be easily transmitted from person to person 鈥� the key step that might lead to a global human flu pandemic that could kill millions. 鈥淭he virus died out 鈥� it didn鈥檛 go beyond the family. Like other cases of human-to-human transmission, this was a dead end,鈥� said WHO spokesman Dick Thompson.
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The case was the first human-to-human transmission of H5N1 to be confirmed by laboratory tests, he added. A 鈥渢iny鈥� genetic change in the virus was found in samples from two of the victims, allowing scientists to identify the chain of transmission. 鈥淲e鈥檝e never really had a fingerprint to confirm human-to-human transmission like we had here,鈥� Thompson said.
Detective work
Until now, about half a dozen instances of human-to-human transmission of the H5N1 strain of the avian influenza virus have been confirmed, but only by eliminating other possible causes of infection. These cases mainly involved relatives or close carers who were infected by someone who had caught the virus from poultry.
The WHO announced the new case in Jakarta, Indonesia, on Friday, confirming earlier suspicions that an Indonesian woman had transmitted bird flu to several members of her family (see Bird flu may have passed between family members).
杏吧原创s are investigating two differences between the new human cluster and previous cases. One is its relatively large size: in other instances the virus spread directly from the initial victim to just a handful of other people.
The other is the discovery through laboratory tests that the father in the family was not infected directly by his sister, the initial victim, but one step further along the chain through a son who had caught the virus.
鈥淭his is something we鈥檝e never seen before either,鈥� Thompson said. However, all the victims were in close contact with each other, and after weeks of monitoring more than 50 of the father鈥檚 other contacts there was no sign that any had bird flu.
