A grayling is the latest fish to test positive for the virus

Fish farms all over the county have already been put into quarantine after the disease was found in Nidderdale.

The latest case of viral haemorrhagic septicaemia (VHS) was found in a sample of grayling from waters below the trout farm where it was first confirmed.

Defra said there were no implications for human health from the virus, which affects mainly farmed rainbow trout.

It also said there had been no more cases of the disease on trout farms but further checks were under way.

The infected fish showed no clinical signs of the disease but government scientists are continuing to test wild fish in the river both below and above the infected farm.

It added that although there was no scientific evidence that VHS caused significant outbreaks of disease in wild freshwater fish stocks, any persisting infection in wild fish could infect or re-infect trout farms in the area.