Assalamoalaikum ! Here is an authentic dua for fever and illness from hadith. If you or anyone form your relatives/family is suffering from fever, this dua can do the trick for you. The dua is mentioned in Abu Daud and can be recited for any type of fever.
اَسْأَلُ اللّٰہَ الْعَظِیْمَ رَبَّ الْعَرْشِ الْعَظِیْمِ اَنْ یَّشْفِیَکَ
As-alallahul azeema rabbal arshil azeemi an yash-fiyak
There are other beautiful duas particularly for the problem of fever and sickness/illness. As mentioned in a hadith narrated by Aisha RA (May Allah be pleased with her), Prophet Mohammad Peace Be Upon Him used to recite Surah Falaq and Surah Naas when he felt sick or had fever. Surah Falaq and Naas are a good remedy if you don't want to memorize other duas due to difficulty in understanding the Arabic text or memorizing them as these two surahs are usually recited by almost every Muslim in salah.