leaning towards flu

We started letting him out and about more last week. I didn't think anything of it when the headache started yesterday. This morning after waking up he has a slight fever and has been sick at his stomach. So now we are watching him and it may be a virus or flu. Which is better than another cause so we will take it. Probably picked up a bug last week because his immune system still isn't very strong. He feels terrible which I don't like but I would much rather it be flu or virus than related to other issues.