Fig. 4From: Epidemiological and virological surveillance of influenza viruses in China during 2020–2021Phylogenic tree of the NA gene of the global B/Victoria lineage viruses from 2020 to 2021. NA sequences after removing duplicates and incomplete coding regions, a total of 4743 sequences were used, including 1137 sequences in the mainland of China. The red bar denotes the distribution of viruses collection months. Asia countries excludes the mainland of ChinaBack to article page