On his VDU's blog, Dr. Ian Mackay his talent for making events intelligible: H7N9: the dotted lines that make sense of things... Excerpt:
The latest H7N9 case-per-day chart shows that the trickle of human cases of confirmed avian influenza A(H7N9) virus infection is becoming a drip. The tap? My money is still mostly with the market closures. What precisely in the markets? Dunno, but the consensus seems to be poultry; songbirds look pretty good too, though.
It doesn't have to be, and is unlikely to be, just 1 thing of course. We know that this virus, as with other avian influenza viruses, can be shared around among bird species. It can even go into a human and that isolate be used to infect a bird again. See my recent post on some of this.
What's also particularly intriguing, among the many interesting aspects of H7N9's acquisition and spread among humans, is that we're seeing much more "shouldering" in the Wave 2 epidemic curve than we did in Wave 1's.
Instead of the precipitous decline we saw back in 2013, we're seeing a drop down to ~10 cases per day, but then a slower decline the rest of the way. Is this because we started human cases from more sites this time around? because markets took longer to close after the cases numbers began to climb?; is it related to markets being closed at different times, in different ways, in different locales? Who knows?