A mosquito-borne virus linked to the group of viruses that can cause yellow fever and West Nile virus has been discovered in Scotland for the first time.
The usutu virus, which is transmitted by mosquitos and carried mainly by wild birds, was identified in blackbirds on the Isle of Arran through a national bird surveillance programme.
Locals on the island raised the alarm after seeing a cluster of blackbirds that had displayed “neurological signs” or were found dead during the summer of 2025.
The Animal and Plant Health Agency (APHA) said the virus has been known to cause “significant” blackbird population declines in many European countries, including the UK.
The virus has been circulating in the south-east of England for six years but the agency stressed there have not been any human cases to date and that the risk to the public remains “very low”.
They added that usutu, which stems from the same group of viruses which can cause dengue, yellow fever and West Nile virus, very rarely causes symptomatic disease in humans.
Andra-Maria Ionescu, manager of the APHA national reference lab for vector-borne diseases, said: “The detection of usutu virus in blackbirds in Scotland shows that countries further north are now facing an increased risk of mosquito-borne viruses.
“These findings highlight importance and need for improved, nationwide wild bird and mosquito surveillance to better assess the risks posed to animal and human health.
“APHA continues to remain at the forefront in the fight against this disease.”
The surveillance programme was conducted by the vector-borne disease group at APHA in collaboration with Scotland’s Rural College (SRUC) Veterinary Services and the Mosquito Scotland research programme, led by the University of Glasgow.
Professor Heather Ferguson, Mosquito Scotland project lead at the University of Glasgow, said: “Mosquito-borne diseases are increasingly likely to get a foothold in the UK, including in Scotland, as our environment continues to change.
“In Scotland, we should take this finding as an opportunity to invest in robust surveillance symptoms to boost preparedness for detection and response.
“It is fortunate that this detection of usutu in Scotland has coincided with when the Mosquito Scotland project is running.
“When news of suspicious blackbird deaths consistent with usutu came through, we were able to almost immediately deploy a team of experts to Arran for rapid follow-up and investigation.
“This allowed us to confirm the presence of several different mosquito species near the locations where infected birds were found, including several known to be capable of spreading usutu.”
The APHA urged the public to continue reporting any dead birds, particularly songbirds, owls or any bird showing neurological signs.
It is also encouraging people to keep their gardens free of any stagnant water to minimise any mosquito breeding grounds – particularly during the mosquito active season which runs from April to October.
For information about how to report dead birds visit: www.gov.uk/guidance/report-dead-wild-birds
