As I've suggested earlier, the widespread use of sensitive molecular detection methods, not just on the cases with the most severe clinical signs and symptoms, is absolutely essential to detect mild or asymptomatic cases of infection. The use of PCR in this way seems to have done just that.
I'll keep a close eye on this story but I suspect it will result in a drastic change to the landscape of detection numbers and epidemiology.
Symptoms alone tell only a small part of the story of any respiratory virus. This may strengthen the case for H7N9 having been in the community for much longer than the pneumonia cases officially commencing back in Feb, suggest.