The 82-year-old was seated for dinner on Friday night in Dordogne, southwest France, when the virus emerged, local media reported.
So he started crushing her with an electric racquet designed to kill insects – not realizing that a gas canister was leaking into his house.
The reaction between the racket and the gas set off an explosion, destroying the kitchen and part of the roof.
Fortunately, the octogenarian suffered only a slight burn to his hand.
He is staying at a local campsite while his family repairs his house in the village of Parcoul-Chenaud, according to the Sud-Ouest media.
The fate of the fly was not known.