A low fever all the time does not determine what disease it is. If the temperature of a low fever is only 37.0°C at the maximum, it cannot even be called a fever, and it is likely that there is no disease at this time. The temperature of a low fever must reach 37.3°C or exceed this value, and as long as it does not exceed 38.0°C, it is considered a low fever. The temperature of a low fever is not usually fixed at this value, it fluctuates and only reaches this level at the peak, at other times it can be a completely normal temperature, it is unlikely that a low fever lasts for too long. The first thing to consider is still infectious disease. Clinically, there are many patients with fever who, after searching for various pathogens, are able to identify pathogens that are not too common and cause chronic infections, such as EBV and cytomegalovirus, but there are factors that lead to hypothermia that are considered infectious and cannot be identified, which is called unexplained fever. In addition to infectious factors, non-infectious factors should also be considered, such as autoimmune diseases. If the fever remains low, between 37.3 and 38.0°C, and the cause cannot be found, treatment can be given, mainly symptomatic treatment.