One sample was positive from s wholesale market in the city of Dongguan, which had previously (see post on 28.04) been positive for an H7 virus that was not H7N9.
Previous testing of 542 poultry workers (method unknown) in Guangdong had not identified H7N9 infection. As ProMED noted, in "AVIAN INFLUENZA, HUMAN (71): CHINA H7N9 UPDATE", this makes animals sentinels, instead of humans, for H7N9's presence for the first time during this outbreak.
Shows the benefits of screening for virus without relying on symptomatic presentations hmm?