The company said in a statement that the infected construction worker was involved in a project to improve anti-terrorism defences, which is part of work being carried out under stricter standards for nuclear power station operations introduced after the 2011 Fukushima earthquake and tsunami.
All civil engineering work at the nuclear station, which has two commercially operational units, was halted on the night of 14 April and the company said it does not know when it can restart the project.
The completion deadlines for the upgrade work are August 2022 for Unit 3 and September 2022 for Unit 4.
The infected worker is a male employee in his 50s of construction company Obayashi Corporation, Kyushu Electric said.
After the utility was informed about the infection by the construction company, it ordered about 300 other workers who may have come in contact with their infected colleague to stay home. They include Kyushu Electric employees and those commissioned to work on the anti-terrorism safety project.
The company said the infection would have no effects on the operations of the nuclear power station.
Both units at Genkai resumed commercial operation in 2018 and according to Kyushu Electric’s website are operating normally.