Why is there a high risk of epidemic situation in Longxi County, Gansu Province?

Some communities in Longxi are at medium and high risk. Most places are low-risk. Some time ago, the epidemic was serious and it was closed for half a month. It has been unsealed for a week now. You are free to go in and out anywhere. Wear a mask when going out and scan the code at any time. Of course, you need to scan the code in advance when you come back from other places.