Based on the February 2018 report of the Worldwide Influenza Center (https://www.crick.ac.uk/sites/default/files/2018-07/crick_feb2018_report_for_the_web.pdf, accessed on 6 November 2023), it can be concluded that NA of A/H1N1 viruses underwent minimal evolutionary changes from 2013 to 2018, but A/H3N2 viruses circulating since 2016 acquired a N-linked glycosylation site in N2 at position 245 which is close to the enzymatic site and can sterically shield NA-inhibiting antibodies [47,48]. The gene discussed is XK; the disease is influenza.