This time we learn that nucleic acids were detected so RT-PCR methods are in use, at least in Zhuhai city, a prefecture-level (between less populated than a Province but more than a County) city on the coast of Guangdong province bordering with Macau.
Was RT-PCR in use during those huge poultry screening events last year? Tracking back to a post on some of the vast numbers of animals tested (hundred's of thousands) earlier in 2013 it looks like the testing back then was virological (trying to grow virus I presume) and serological (detecting antibody to recent infection by the virus) rather than molecular (PCR-based). I stand to be corrected on that.
Just thinking out loud, but it seems to me that 800,000+ birds had been tested using RT-PCR then we would have had a much better idea of the extent to which H7N9 was distributed across China.
As an aside, the 3 most recent human cases also read like a who's-who of 2013's H7N9 hotspots; Jiangsu province, Shanghai municipality and Zhejiang province.
I'm making some more lines available on my Excel sheet.