If the fever has come back, then other possibilities like enteric/typhoid fever need to be ruled out. Usually, if the diarrhoea is associated with fever, the chances of typhoid fever are high and for ruling out the same, tests like a blood culture and typhidot help. Other tests like CBC, an X-ray of the chest, and peripheral smear for malarial parasite etc should also be done. I sincerely hope that helps. Take care.