Hello. I have gone through your question and understand your concern. In my view high fever, headache and joint pain suggest viral infection. As you are travelling, make sure that your child gets a fresh air and is seated comfortably. High fever can cause convulsions in children so make sure temperature is in control. Start with medicine to reduce fever like Calpol or Nurofen or Advil with dose you usually give according to body weight. A sponge bath is also suggested when fever is high. Sponge bath is very simple yet effective way to reduce temperature using lukewarm water. If fever does not subside in three days or symptoms get worse with time, get medical help. Good luck. Hope your concern is answered. Thank You.