Chills and fever can refer to a variety of medical conditions characterized by an increase in body temperature and shivering or chills. Some of the synonyms for chills and fever include pyrexia, febrile illness, temperature spikes, and cold sweats. Chills and fever can be caused by a number of factors, including infections, inflammation, and autoimmune disorders. Additionally, certain medications and environmental factors can trigger chills and fever. If you experience persistent chills and fever or other symptoms such as headaches, muscle pain, or fatigue, it's important to seek medical attention to determine the underlying cause.