Infected case growth has slowed down primarily because of the quarantine of Hubei province. The virus has up to a two week incubation period, and today two weeks later we're able to result of this quarantine. Case growth in Hubei has slowed down.
The issue now is that every major city in China has local infection clusters, and these infection clusters are growing exponentially.
https://i.imgur.com/lQcyqAX.jpg
Even if the net case growth rate is decreasing, the situation is less under control than ever before. Look at China's actions; they're past containment methods and now acting on mitigation.
https://en.wikipedia.org/wiki/2019%E2%80%9320_Wuhan_coronavi...
The Wikipedia page says:
"On 6 February, the Chinese National Health Commission started to change how cases were reported – asymptomatic carriers, who tested positive for the virus but did not show clinical symptoms, would no longer be included in the number of confirmed cases. This had the effect of reducing the total number of cases reported, but also meant that potentially contagious individuals were ignored in reports."
Wuhan is nearing the top of its S-curve, while other cities are still near the start. As such it would make sense for the number of cases to slow down even if it isn't actually being stopped.