The avian influenza virus (AIV) usually only infects birds, but some variants, such as A(H5N1) and A(H7N9), have caused serious infections in humans. While there’s a lot of information about the virus in some areas, little is known about places such as Antarctica, and so researchers have been using the polymerase chain reaction (PCR) to fill in the gaps.
During January and February 2013, an international team of researchers took swabs from 301 Adélie penguins from two sites in the Antarctic, and blood samples from 270 of these birds. They analysed the blood samples using real-time reverse transcription PCR (also known as qPCR). The research was published in the journal of the American Society for Microbiology, mBio.
The team found that 43 (16%) of the 270 penguins carried influenza A antibodies in their blood, and detected AIV genetic material in 2.7% of the samples, six from adult penguins and two from chicks. The penguins turned out to be infected with A(H11N2) subtype AIV. This is the first time that an AIV has been identified in penguins or other birds in Antarctica.
Of the virus samples found, four could be cultured, confirming that the virus was live, but it did not cause infections in ferrets. Looking at the genome sequences of the four viruses more closely, the researchers found that the virus subtype is unlike any of the currently known avian influenza viruses anywhere in the world.
“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,” says Aeron Hurt of the WHO Collaborating Centre for Reference and Research on Influenza in Melbourne, Australia.
Analysis of the gene segments showed that four of these were most closely related to North American avian lineage viruses from the 1960s to 1980s, and two had a distant relationship to a large number of South American AIVs from Chile, Argentina and Brazil. Looking at evolutionary rates, the researchers suggested that the virus has been evolving for the past 49 to 80 years.
While the virus did not cause illness in the penguins, Hurt said the results showed that avian influenza viruses could get down to Antarctica and be maintained in penguin populations. Unanswered questions include how often AIVs are 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. It highlights the potential risk of an introduction of highly pathogenic AIVs into the continent.