Complex sentence: Later on (day 5 to day 10 from the clinical onset), temperature will lower to a normal range (38.0-39.5 ° C), but the disease will continue to progress, despite a possible apparent clinical improvement (appetite comes back).
Split into simpler sentences: Later on (day 5 to day 10 from the clinical onset), temperature will lower, to normal range (38.0-39.5 ° C). But, the disease continue to progress, despite a possible apparent clinical improve (appetite comes back).