Hi welcome to Health care magic forum. Keeping aside the other factors, you should be concerned about, the shaking and freezing. It could be malaria
, or ac urinary tract infection
, or some other infection.
If the infection is very severe, there the fever
may not be appearent, the body may not become hot. So to get confermation of what sort of infection is there ,you must consult a physician for diagnosis and treatment.
Besides i advise you to follow some diet recommendations as give him more of green leafy vegetables, pulses, sprouts, fruits, milk, egg, meat, and seafoods , to provide suffecient nutrients to body to provide resistance and general health, to fight with such infections.
wishing him a quick recovery and thanks for calling.