Student or Learner
I would like to know the difference in the meaning between "1" and "2".
1. I am sick with flu.
2. I have been sick with flu.
Also, in #2 your sickness may be finished, you might be feeling better now.
A: What's the matter?.
B: I am sick with the flu.
A: Why haven't you been working for the past week?
B: I have been sick with the flu.
In both cases, the person is still sick with the flu. (If I had been sick but I no longer am sick, I would say I was sick.)
Context is always important.