A Swiftair Avions de Transport Regional ATR-72-200, registration EC-KJA performing flight WT-1275 from Belgrade (Serbia) to Cologne (Germany), was enroute at FL220 over Germany near Frankfurt/Main (Germany) when the first officer became incapacitated. The captain diverted the aircraft to Frankfurt for a safe landing about 25 minutes later. Germany's BFU rated the occurrence a serious incident and opened an investigation. On Apr 4th 2017 the BFU reported in their December Bulletin, that the first officer noticed first symptoms of a flu-like infection after reaching cruise level, which increased over the next two hours. About 30nm southeast of Frankfurt enroute at FL220 the first officer suffered a hyper ventilation tetany which could not be stopped anymore. The crew therefore decided to divert to Frankfurt, the captain declared PAN and received direct vectors for a landing on runway 25C at Frankfurt/Main. During first medical aid the body temperature of the first officer was measured at 39.5 degrees C, he was taken to the airport clinics. Following a night in the clinics he was discharged with a suspected diagnosis of flu-like infection.