These results will start to unravel how long this virus has been circulating in Shanghai (it takes a couple of weeks to "seroconvert"; show a jump in specific antibody levels in the blood; looking in any older paired sera repositories would be great too) and also how many cases, beyond the one child so far reported, of moderate, mild or asymptomatic infection there could have been.
Increasing that denominator is a great way to put the ability of H7N9 to cause severe illness in much clearer perspective.
