Can any of them come infected by the COVD-19?
The probability is very low. Almost all of the participants will come from areas where the presence of the COVD-19 is nil or extremely low.
By comparison, a number of passengers equivalent to three times the MWC go through the airports of Atlanta or Los Angeles, two times pass through the airports of London, Paris or Amsterdam each day, and 1.5 times through Madrid and Barcelona each day. And none of them closed so far.
The basic hygiene measures (handwashing, not sneezing or coughing to the open) and common sense are more solid and effective.
If we follow the same line of thinking (we shouldn't), we would have to close all the airports tomorrow.
edit: typo
I don't think this is known or knowable at the moment. Hence the worry.
You are right that airports are probably a greater risk. Perhaps they should be closed. On the other hand, that would be far more disruptive.
As for basic hygiene, yes, we all should. At the same time, we all know that a significant fraction of the population can't or won't do this.
Edit: Here's the proper method: https://www.who.int/gpsc/clean_hands_protection/en/
A significant caveat is that the sink/restroom must allow proper handwashing. Many lack paper towels, for example. If you have to touch the faucet handle or the door after you start washing (which takes two minutes), the method has not been followed. It's harder than it looks.
[1]: https://gisanddata.maps.arcgis.com/apps/opsdashboard/index.h...
It only takes one person leaving without washing their hands for the irony to be apparent.
Holding MWC without Huawei, ZTE, BBK, Xiaomi and co. is pretty much meaningless
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.
No idea whether the conference should be cancelled, but it's not an irrational idea. There could be a large number of silent cases outside of China already.