Self-resistance is not recommended for adults with a fever of 40°C. A prolonged fever of 40°C must be seen promptly at a hospital infection unit. Fever is a normal defense mechanism of the body, and treatment is usually required when the human body temperature exceeds 38.5°C. Adults with a fever of 40°C will experience significant discomfort and may also experience dizziness, blurred consciousness or mental confusion. Adults with a fever of 40°C need to be treated for the specific cause of the illness. If the fever is caused by a bacterial infection, anti-infective treatment with drugs that are sensitive to bacteria can be given, along with physical cooling. If fever of 40℃ persists, symptoms such as ketonemia, reduced secretion of digestive juices, reduced activity of digestive enzymes and gastrointestinal disorders may occur, and may even lead to shock or multiple organ failure. Therefore, adults with a fever of 40℃ need to be seen in a hospital infection clinic in a timely manner, and symptomatic treatment should be carried out after examination and confirmation of the cause to prevent delay, as well as timely hydration to avoid dehydration and close monitoring of temperature changes.