The epicentre of deadly bird flu outbreaks has shifted from Asia to Europe and Africa, a new study has found.
For 25 years, bird flu viruses typically emerged from Asia, but major changes in the virus and its spread among wild birds mean the outbreaks are shifting. Research shows that while outbreaks in 2016 and 2017 started in China, two new H5 viruses emerged in 2020 in African poultry and in 2022 in European wild birds.
“These results highlight a shift in the HPAI [highly pathogenic avian influenza] H5 epicentre beyond Asia,” researchers write in the paper published in Nature.
The latest outbreak of the highly infectious variant of H5N1 caused Europe’s worst bird flu outbreak, before spreading globally. It has now reached every continent except Oceania and Antarctica, killing record numbers of domestic and wild birds, and even jumping into mammals. It can also jump to humans: since 2003, H5N1 was found in 873 humans, resulting in 458 deaths, according to the World Heath Organization. Most cases were linked to the handling of infected poultry, and it is not known to be able to transmit from human to human.
An international team of scientists led by the University of Hong Kong analysed outbreaks between 2005 and 2022, collecting data on confirmed cases from the Food and Agriculture Organization and the World Organisation for Animal Health. They also studied 10,000 sets of viral DNA.
Despite the number of outbreaks, only 0.2% of cases were sequenced, researchers said, and urged countries to increase surveillance to understand how the virus is changing. Monitoring infrastructure is particularly weak in Africa, they said. The authors suggest the increasing persistence of avian flu in wild birds is driving the evolution and spread of new strains.
Bird flu is highly infectious, with scientists saying one bird can infect as many as 100, with the virus present in faeces, mucus, blood and saliva. UK government authorities say more than 99% of cases in poultry in the UK have come from wild birds.
Mass culling used to be an effective policy to control the disease’s spread in poultry, but because avian flu is now so widespread in wild bird populations, this is proving less effective.
The spread of bird flu within the poultry industry is determined by human activity and how birds are traded. In wild birds, migratory flyways are key indicators of where the disease will spread, with key migration routes along the east Atlantic and Pacific flyways, meaning it has been able to spread to new areas that have never been exposed to it before.
Working out how many wild birds have died is difficult because so many carcasses are never found or counted, but researchers say it will be in the millions.
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