I keep thinking that my wife is going to die; is this normal?

Whenever my wife leaves the house, goes on a road trip, or if we are apart, I can’t help but thinking that she might die. I don’t think (and I could be wrong) that this is a phobia for I am not greatly unsettled about the thought. I don’t feel anxious or worried, just confused. When I think about her being gone, I am not happy about it. Is this normal, or what?