An unusual type of bird flu has been found in penguins in Antarctica, with Australian researchers saying it raises many questions.
A new kind of bird flu has been detected for the first time in Adelie penguins in Antarctica, though the virus does not seem to make them sick, researchers say.
The virus is unlike any other avian flu known to science, said the report published on Tuesday in mBio, a journal of the American Society for Microbiology.
"It raises a lot of unanswered questions," said study author Aeron Hurt, senior research scientist at the World Health Organisation Collaborating Centre for Reference and Research on Influenza in Melbourne, Australia.
The findings show that "avian influenza viruses can get down to Antarctica and be maintained in penguin populations", he said.
The study is the first to report on live avian influenza virus in penguins, though previous research has found evidence of influenza antibodies in penguin blood.
But it remains unclear how often various strains of bird flu are introduced into Antarctica, whether the deadliest types could make it there, and which animals or ecosystems allow the virus to survive.
Hurt and colleagues collected samples from about 300 Adelie penguins at Admiralty Bay and Rada Covadonga during January and February 2013.
They found live, infectious avian influenza virus in eight samples, or nearly 3 per cent of the birds. The penguins did not appear to be sick.
All the samples were found to be H11N2 influenza viruses that were highly similar to each other.
But when researchers compared the genome sequences of four of the viruses to a publicly available database of animal and human viruses, "we found that this virus was unlike anything else detected in the world", said Hurt.
"All of the genes were highly distinct from contemporary AIVs (avian influenza viruses) circulating in other continents in either the Northern or Southern Hemisphere."
One well known kind of bird flu is H5N1, which is believed to be carried by migrating ducks.
About 650 people have been infected with H5N1, and about 60 per cent have died, according to the World Health Organisation. It is also highly lethal to domestic poultry.