Human seasonal reassortant A(H1N2) influenza viruses harbouring the HA gene from an A(H1N1)pdm09 virus and the NA gene from an A(H3N2) virus were detected in one case in Sweden in December 2018 and one case in the Netherlands during the 2017/18 influenza season [4,5]. The gene discussed is XK; the disease is influenza.