About 860 tons of cultured carp have died since October in two lakes in Ibaraki Prefecture from the herpes virus in the first such case in Japan, the prefectural government said Sunday.
The carp began to die in early October and the number of deaths jumped in the middle of the month, according to prefectural officials. The virus has been detected in samples taken from the dead carp, they said.
The prefecture has not been able to locate the route of infection.
The damage from the deaths of some 660 tons of carp in Lake Kasumigaura and another 200 tons in Lake Kitaura is estimated at 150 million yen, they said.
The virus cannot be transmitted to humans and consumption of infected carp would not have any ill effects, the officials said.
The virus was first detected in 1997 in Israel and has been found in Belgium, Britain, Germany, Indonesia, the Netherlands, Taiwan and the United States. In an attempt to prevent infections, Japan has imposed restrictions on carp imports July 14.