XK and influenza: Influenza pseudotypes bearing HA and NA envelope glycoproteins devolved from the rest of the virus have been demonstrated to be ideal tools to monitor the effects of viral evolution on serological outcomes and can be used in parallel with other serological tests (HI, MN, and SRH), for accurate sequence-directed, sensitive, and low-containment assays for measuring antibody responses against influenza H5 and H7 HA and/or NA.