You just described what my youngest 2 children have been sick with this past week.Supposedly its just a virus that needs to run its course.There's several students and teachers that's out sick with this at my kids school.What shocks me is how fast this virus hits.Both of my kids have been playing and happy then took a nap and woke up with a terrible headache,fever,etc.One good thing my kids naturally do when they're sick is go into fasting.I dont worry nearly as much as long as they're taking liquids.Now if someone would just tell my MIL that they dont need tylenol crammed in them at the first sign of a fever!:)