OK, I thought about that. But you could also say just "teşekkur ederim nasılsınız" couldn't you? Thats why I thougth there should be an emphasis on "you" (siz). Is it wrong?
There is no doubt that this means "Thank you, how are you?" The question is : is it OK to emphasize the you with "and you?" even though it's not needed, and probably totally unnecessary, as merdogan says.