The antonyms for the word slow fever include fast, rapid, hasty, quick, and swift. According to medical experts, fever is a common symptom of an underlying infection, illness, or disease. A slow fever is a low-grade fever that typically lasts for several days, indicating a mild infection or inflammation in the body. In contrast, a fast fever is a high-grade fever that develops rapidly and may indicate a severe infection, such as pneumonia or meningitis. Rapid, hasty, quick, and swift fever all imply a sudden onset and a fast, intense course of the illness. Furthermore, these antonyms illustrate the severity and urgency of the medical condition, requiring prompt medical attention and treatment.