Red squirrels could be almost wiped out in one of their last British strongholds by the deadly squirrel pox virus. Squirrel pox, carried by invasive grey squirrels, has helped destroy 95 per cent of native reds in England and Wales since 1952. But it had never been seen on Anglesey, Wales, raising fears after a dead red squirrel with facial lesions typical of the disease was discovered on Wednesday. Squirrel pox, carried by grey squirrels, has helped destroy 95 per cent of native reds in Britain since 1952. The virus is completely harmless for the invasive greys, which were introduced to Britain from America in 1876.