The process of getting on and off is very crowded. If you don't take personal protective measures in the process of crossing, the chances of being infected are very high. The longer you take off your mask to drink or eat, the greater the chance of being caught. The confirmed case touched the door handle when going to the toilet, and others may also come into contact with the virus from the door handle when entering and leaving. If hand hygiene is not done in time, they may be infected. The journey takes a long time, and if you occasionally pull down the mask on your seat or don't wear it correctly, you may be exposed to the virus and cause infection.
Therefore, it is necessary to isolate or re-nucleic acid when the train leaves the station.