Virus carried to UK by mosquitoes ‘has killed up to 40% of local blackbirds’

A mosquito-borne disease whose spread is fuelled by climate change is decimating blackbird populations in parts of Britain, scientists have warned.

The deadly Usutu virus, first discovered in southern Africa 80 years ago, has been spreading around Europe over the last three decades.

It was detected for the first time in the UK in 2020, when several blackbirds in the London area were found to be carrying it following that year’s summer heatwave.

Since then, the Greater London blackbird population has declined by around 40%, according to Dr Arran Folly of the Animal and Plant Health Agency (APHA).

It has been detected as far west as Dorset and as far north as Cambridgeshire.

‘We’ve seen that the virus has spread further than we thought it might do, and it’s persisted,’ Dr Folly told the BBC.

Blackbirds are particularly vulnerable to the virus, though other wild birds are also at risk.

The APHA has been tracking mosquito-borne disease in wild birds for decades.

Researchers have warned that longer summers, hotter temperatures and heavy rainfall are increasingly turning Europe into a ‘breeding ground’ for mosquitoes.

There have been no reported human Usutu cases in the UK, though 46 infections had been confirmed across the rest of Europe as of 2019.

Patients mostly experienced no symptoms, though some people with compromised immune systems experienced neurological symptoms such as encephalitis.

Dr Folly said his team’s finding ‘gives an indication that in the future we might get other viruses that are transmitted by mosquitoes emerging in the UK’.

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