Oh bless.... I know alot of people with similar symptoms at the moment. So I wouldn't worry too much but certainly keep an eye out just in case. Usually recovered with 4 to 5 days if it is the same thing.
Hope he feels well soon.
Has he got teeth coming? I know it's an old chestnut but can often explain otherwise inexplicable symptoms.
There are a lot of nasty bugs going around the littlies at the moment though.....