Poultry workers had no prior exposure to H7N9 [UPDATED]

Bai and colleagues report in NEJM that 1,544 samples collected from young adult poultry workers between Jan-Nov 2012 in 4 key provinces/municipalities of China (municipality of Shanghai, Zhejiang province, Jiangsu province and Anhui province) were tested using a haemagglutinin-inhibition (HAI) assay and a microneutralization (MN) assay. 

The HAI assay found some weak reactivity (antibody was positive when diluted as far as 1:40), but no neutralizing antibodies were found by MN test. 

This is chapter 1 of a story that next needs to include more contemporary testing. 

The first part reveals no assay-specific antibodies present in these close contacts of poultry, prior to late 2012; before the H7N9 outbreak.