do you realize that small pox is a deadly disease? It's hardly the type of thing you ask about casually. If someone has a very serious illness, you don't expect it clear up in a couple days. You don't need to even mention what the disease is - the person will certainly remember what it is they have. "How are you feeling these days?" "How are you doing?"
I know we ask about "something" e.g. I asked about the book; He asked about the sun; I asked about Bob, etc.
But in the above context, I cannot understand "ask about casually"? Please explain to me how it has been used.