Image copyright Kim Steele/Thinkstock Scientists are warning of new threats to penguins on Antarctica from diseases spread by migratory birds.
A modern strain of bird flu has been found in penguins living on the snowy continent, although it does not seem to be making them ill.
Conservationists say penguins need better protection through monitoring for new diseases and safeguarding their breeding and fishing grounds.
Bird flu is an infectious disease of poultry and wild birds.
Scientists found an unusual strain of bird flu among penguins on Antarctica a few years ago.
A second strain has now been discovered, suggesting viruses are reaching the continent more often than previously thought.
Fragile Earth
"This is a concern because avian influenza viruses __that can be deadly in many birds have recently circulated in North America," said Dr Aeron Hurt of the Peter Doherty Institute in Melbourne, who visited the continent to survey penguins and other birds.
He said the virus discovered did not seem to cause any illness in the birds, but the fact __that it is down on the Antarctic Peninsula showed there was potential for deadlier viruses to also travel there.
"The impact of a pathogenic influenza virus, one that causes death or severe illness in birds, would have a really devastating impact," he added.
The Antarctic Peninsula is too far south to be part of the main flyways across the world for migratory birds.
However, a few birds do migrate there from North and South America.
Experts say a better understanding is needed of how viruses reach the continent.
Unique birdlife
Rory Crawford, seabird policy officer of the RSPB, said penguins were the second most threatened group of seabirds after albatrosses, so any new potential threats were of concern.
"Every effort needs to be made to prevent future transmission and its potential impacts on the unique birdlife of Antarctica," he said.
"Further, broader penguin conservation needs to be stepped up to help these imperilled birds - including through the protection of breeding habitat, identification and proper protection of marine protected areas and appropriate fisheries management."
Dr Derek Gatherer, of the University of Lancaster, said the findings suggested that the bird flu had originated in the northern hemisphere and entered Antarctica recently.
"Penguins are therefore under threat from highly pathogenic avian flu, despite their isolation," he said.
The research was published in the Journal of Virology.
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