Afotimber
The highly pathogenic avian influenza (HPAI) H5N1 virus has been confirmed on sub-Antarctic Marion Island, raising concerns over its impact on local wildlife.
The Department of Forestry, Fisheries, and the Environment announced that samples collected between September and December 2024 were transported back to mainland South Africa via the SA Agulhas II last month. Polymerase chain reaction (PCR) testing conducted in March confirmed infections in six bird species: wandering albatross (Diomedea exulans), king penguin (Aptenodytes patagonicus), brown (Subantarctic) skua (Stercorarius antarcticus), southern giant petrel (Macronectes giganteus), northern giant petrel (M. halli), and sooty albatross (Phoebetria fusca).
Among the affected species, wandering albatross chicks have been significantly impacted, with at least 150 of approximately 1,900 chicks from the 2024 cohort reported dead. However, adult birds have suffered the highest mortality rates in other species. The department confirmed that at least 80 adult brown skuas and 120 adult king penguins have died, along with smaller numbers of giant petrels—20 southern and four northern—and five sooty albatrosses.
“The deaths of adult seabirds are of greater concern than chicks because most species only start to breed at three to ten years of age, and most affected species raise at most one chick per year,” the department stated. It further noted that seabirds already face multiple threats, including fisheries bycatch, climate change, plastic pollution, and predation by introduced house mice on Marion Island.
Following an initial suspected HPAI case in a brown skua exhibiting clinical symptoms—such as twitching and tremors—in mid-September 2024, similar cases emerged in early November, with mortalities continuing into March. “Though the overall death rate slowed significantly in January, the reduced mortality rate is promising, but as the bird species and age composition varies throughout the year, it is difficult to predict how the outbreak will progress,” the department explained.
“The potential effects on marine mammals are also of concern, but no increased mortality has been reported in any mammal species so far,” the department added.
Marion Island, alongside Prince Edward Island, serves as a critical breeding and moulting ground for millions of seabirds and marine mammals, including nearly half the world’s wandering albatross population, hundreds of thousands of penguins, and large numbers of southern elephant seals and Subantarctic and Antarctic fur seals. The archipelago, situated in the southwestern Indian Ocean approximately 2,000km southeast of Cape Town, plays a vital role in global biodiversity.
The department noted that findings from Marion Island could provide insights into potential risks for animals on Prince Edward Island, given the islands’ shared ecological characteristics. Visits to Prince Edward Island occur only once every four years to minimize human impact, with the last survey conducted in November 2023.
HPAI (H5N1) has been spreading globally since 2021. The virus was first detected in seabirds and marine mammals in South Georgia, southeast of South America, in October 2023. It reached the Antarctic Peninsula in February 2024 and was later identified at the French archipelagos of Crozet and Kerguelen—located 950km and 2,300km east of Marion, respectively—in late 2024. The virus is known to be transported across long distances by migrating birds.
“The situation on Marion Island is being closely monitored by the field personnel overwintering on the island, who have been trained to recognize possible HPAI signs in birds and seals, and in the necessary monitoring and mitigation methods,” the department assured. “They will continue to take all precautions to ensure they do not spread the virus. There are few other disease mitigation tools available in this type of situation.”