The Koi Herpesvirus has been found in Long Island Lake, Earith, Cambridgeshire.
Since first being discovered in Israel in 1998 the disease has spread round the world and has no known cure.
So far only carp are infected by the illness which lies dormant in the fish until factors like stress bring it on.
Typical symptoms of infected fish, including breds like common, mirror, ghost and koi are lethargy, erratic swimming behaviour and increased mucus production
The area includes the Earith Carp Lakes and the Environment Agency is currently on-site disinfecting angling equipment and entrances.
Luke Walsh