So when do we shut down air travel?

Chinese cities cancel New Year celebrations, travel ban widens in effort to stop coronavirus outbreak

https://www.washingtonpost.com/world/coronavirus-china-wuhan-latest/2020/01/23/2dc947a8-3d45-11ea-afe2-090eb37b60b1_story.html

5 cities now? 12 countries? 14 people in uk being tested