Why did Shanghai receive the SMS reminder of Nanjing 1 10 on epidemic prevention?

Maybe you have been to Nanjing recently, or your number is from Nanjing.

Close contacts refer to people who have close contact with suspected and confirmed cases of the virus and have not taken effective protection two days before symptoms appear, or two days before samples of asymptomatic infected people are collected. Including * * * the same resident, medical staff in medical activities that may produce aerogel environment, people who eat or entertain in a closed environment, people who have close contact in the same place, people who visit cases, other forms of direct contacts, such as the accompanying person of the case, nursing or peers who have close contact with the same vehicle (within 1 m), people who are in contact with the environment and articles contaminated by cases or asymptomatic infected people.