Of the 20,000 juvenile scorpian fish susceptible at the farm in Hutami-chou, Hyogo, the outbreak led to 377 cases.
The source of the outbreak is unknown, but the occurrence of red sea bream iridovirus has terminated with the declining of the seawater temperature.
According to the Manual of Diagnostic Tests for Aquatic Animals (2013), outbreaks have been seen mostly in the summer season at water temperatures of 25°C and above.