Surah Falaq and Naas are the best remedy for fatal illnesses and diseases. The second verse of Surah Falaq is all about seeking God's protection from the evil of every created thing and this also includes health-related issues such as:
All kinds of sickness and fevers
Chronic and life-threatening diseases
Mental illness such as depression, anxiety, bipolar, all kinds of phobia
Anything that negatively impacts a person's health and physical life.