The health officials surely isn't (and won't be) curious about isolated flu-like cases, they can't because there are simply too many such patients, to the point

The health officials surely isn't (and won't be) curious about isolated flu-like cases, they can't because there are simply too many such patients, to the point it is not realistic to track them all. The doctors who saw these cases are certainly curious, but unless one sees a number of related cases with similar symptoms, "novel infectious disease" would not be among the first few explanations one turns to. There are simply too many other possible reasons (and more probable in routines) for flu-like symptoms. Unfortunately due to the nature of this virus early cases are indeed pretty isolated. From what I read, the virus was first detected by an mNGS run in late Dec, which as far is still a "fuck I believe this must be caused by microbe but I'm seriously out of idea what could this be"-thing to Chinese doctors.