Hi Doctor, I Have Twin Sons, One Had Dengue With

Hi doctor,
I have twin sons, one had dengue with platelet count 150000 now it has increased to 250000, but the other twin has fever for more than 5 days with platelet count of 400400 on the first day and he is on antibiotic , but ferver is still persisting as it is the 5th day I am concerned if he will also have dengue!. Please let me know if I have to do the plactelet count after the fever stops or on which day to be done?

Thanks and regards
Lydia