The WHO Chinese National Influenza Center have released three sets of sequences (H7, N9, MP) from two cases in Shanghai (A/ Shanghai/3 /2013 and A/ Shanghai/4 /2013), and one from Jiangsu (A/ Jiangsu/01 /2013). They are to be commended for the rapid release of these important sequences. The two cases from Shanghai had collection dates in late February and early March, suggesting they are from the cases from the Fifth Peoples Hospital in the Minhang District (see map ). Both had H7 Q226L, which is common and bird flu H7N9 sequences from avian and human sources.

However, the Jiangsu sequence, A/Jiangsu/01/2013, has L226I , which was also present in A/ Hangzhou/1 /2013, which was from a chef who worked in Jiangsu, where he was likely infected. Moreover, all three sequences from Jiangsu/1 exactly matched the Hangzhou/1 sequence signaling clonal expansion. The full Hangzhou/1 sequence also had PB2 E627K.

L226I is present in seasonal flu, and signals a human adaptation. It has not been reported in any of the avian sequences, and its presence in identical human sequences raises serious pandemic concerns.