The first one is not correct grammar - for this the third example would be correct.
We use both examples 2 and 3 and the person asking wants to know if the patient has scabies now (#2), and if he had it some time in the past (#3).
However, it's common for a person to ignore the grammar rule and he may use #2 when he should use #3.
In your question, you use we are still having a chance. This is a similar error to the error in example #1: 'have' in these meanings aren't used in continuous because it's used in the sense of possession.
Student or Learner