An international team of researchers has identified a previously unknown avian influenza virus in a group of Adelie penguins from Antarctica. The new virus is described in a study published this week in mBio.

Other research groups have previously detected influenza antibodies in Antarctic birds, but until now no one had detected an actual live influenza virus in penguins, said study author Aeron Hurt (pictured), a senior research scientist at the WHO Collaborating Centre for Reference and Research on Influenza in Melbourne, Australia.

For the study, Hurt collected swabs and blood from Adelie penguins in two locations on the Antarctic Peninsula: Admiralty Bay and Rada Covadonga. Using a laboratory technique called real-time reverse transcription-PCR, the researchers found avian influenza virus (AIV) genetic material in 3 percent of the samples. The researchers were able to culture four viruses, demonstrating that live infectious virus was present.

On further analysis of the samples, the researchers found all viruses were H11N2 influenza viruses that were highly similar to each other. But when the researchers compared the full genome sequences of four of the collected viruses to all available animal and human influenza virus sequences in public databases, “we found that this virus was unlike anything else detected in the world,” explained Hurt. “When we drew phylogenetic trees to show the evolutionary relationships of the virus, all of the genes were highly distinct from contemporary AIVs circulating in other continents in either the Northern or Southern Hemisphere.”

Four of the gene segments were most closely related to North American avian lineage viruses from the 1960s to 1980s. Two genes showed a distant relationship to a large number of South American AIVs from Chile, Argentina and Brazil. Using a molecular clock to incorporate the evolutionary rate of each AIV gene segment, the researchers estimated that the virus has been evolving for the past 49 to 80 years without anyone knowing about it. Whether this evolution has occurred exclusively in Antarctica is currently unknown, Hurt says.

While the virus did not cause illness in the penguins, the study shows that “avian influenza viruses can get down to Antarctica and be maintained in penguin populations,” Hurt says. “It raises a lot of unanswered questions,” including how often AIVs are being introduced into Antarctica, whether it is possible for highly pathogenic AIVs to be transferred there, what animals or ecosystems are maintaining the virus, and whether the viruses are being cryopreserved during the winters.

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