It sounds like he might have meningitis to me anyway. Than average body temp is around 37.0 +/- 1 40.0 is way way to high. You can strip him down to just a nappy then place ice- packs around him they dont not have to touch him.
Ill list the most common systems and you can go through them.
- Tense or bulging soft spot
- High temp
- Very sleepy/staring expression, too sleepy to wake up
- breathing fast/hard to breath
- extreme shivering
- pin ***** rash/marks or pruple bruises anywhere on the body
- sometimes diarrhoea
- vomiting/refusing to feed
- irriatable when picked up
- blotchy skins, getting paler or turning blue
- a stiff body with jerky movements or else floppy and lifeless
- pain/irriability from muscle aches/ serve limb/ joint pain
- cold hands and/ or feet
If this is the case you need to take him back to the the ER straight away. If its a long journey then call for a emergency vic. make sure you tell them you think its meningitis.
Hope he is feeling alot better,