Vikings coach Brad Childress has been vague the past two days when asked what type of illness has kept wide receiver Percy Harvin out of practice. It was unclear if the rookie was even at Winter Park on Wednesday but today reporters saw Harvin make a brief appearance in the locker room before leaving the facility.

My first thought was if Harvin was sick with the flu that he would have been told to stay home. Especially with all the fear about the H1N1 virus and the fact that an infected player could spread the sickness through an entire team.

So why was Harvin allowed at Winter Park to at least do some of the off-the-field work to get ready for Sunday's game? Because it appears his issue is with headaches and more specifically migraine headaches that are so bad they make him sick to his stomach. I'd heard Harvin had an issues with migraines and ESPN just mentioned in a throw-away line on its "NFL Live" show that that was the problem.

If migraines are the issue that might explain why a seemingly healthy 21-year-old like Harvin, a guy who is in outsanding shape, would miss the Vikings' three-day minicamp in May or why he might be sent him sick from the rookie symposium.

Here is an entry from the Mayo Clinic on migraines and just how painful they can be to those who suffer from them.

Harvin, by the way, is listed as questionable for the game against the 49ers.