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3 bird-flu viruses hit Nigeria
05/07/2006 22:31 - (SA)
Malcolm Ritter
Nigeria - Scientists say they've found surprising evidence from Nigeria, the first African nation to report a dangerous form of bird flu, that the virus entered the country at least three times.
But, Yoshihiro Kawaoka, a virologist from the University of Wisconsin-Madison and the University of Tokyo, who hadn't taken part in a study of the virus in Nigeria, said the researchers made a good case for three different introductions of the virus.
He said it was a surprise, because, ordinarily, one would expect the virus to enter just once and later diversify within a country.
Kawaoka said: "Obviously the virus is spreading more efficiently than we thought. Maybe similar things could happen in other countries."
One expert said the H5N1 virus spread more efficiently than researchers had thought.
H5N1 shown up in birds
The new findings in a paper in Thursday's issue of the journal, Nature, did not reveal whether the virus was taken to Nigeria by migratory birds or by imported or smuggled birds.
Albert Osterhaus of the Erasmus medical centre in Rotterdam, The Netherlands, said: "We think the most likely explanation is that it came by migratory birds, but we can't exclude the other possibilities."
It was reported that Nigeria had many bird sanctuaries along two migratory flight paths that connected with southern Russia, Europe and western Asia.
Osterhaus said it was not clear which species of migratory birds might have been involved in possibly carrying the virus.
Nigeria first reported H5N1 bird flu in February, at a large commercial farm that raised chickens, geese and ostriches.
The virus had since shown up in birds at other locations around the country.
The virus could jump to humans and scientists were worried that it might mutate into a form that spread easily and rapidly among people, setting off a deadly flu pandemic.
However, the vast majority of the more than 200 human cases globally so far had come from exposure to infected birds.
'The virus is spreading more'
For the Nature study, researchers compared the genetic makeup of H5N1 virus samples from northern Nigeria and from two farms in southwest Nigeria.
Osterhaus said they found distinct strains that differed so much from each other they probably didn't all arise within Nigeria.
He said the diversity suggested three different strains had entered Nigeria independently, although it was impossible to tell where they came from.
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