The event was December 2015 but agencies reported it later.
A US lab is being blamed for the accidental release of a new strain of flu from a lab in Shelkostantsiya, 30 km away from the city of Kharkov. The strain of flu, called California flu, has killed 20 Ukranian soldiers and hospitalized 200.
Newstarget. April 22, 2016.
Google translated to English the Ukraine Ministry of Health news site. No mention of the flu back to April 15, 2016.
News from MINA. Jan 25, 2016.