Infants with persistent low-grade fever for 2 days should be examined for inflammatory markers such as routine blood tests, C-reactive protein, and calcitoninogen to determine the nature of the infection. If it is caused by bacterial infection, the white blood cells, neutrophils, C-reactive protein and calcitonin will be increased, and antibiotics should be given to treat the infection, and intravenous antibiotics can be used if necessary. If it is caused by viral infection, the above indexes will not be increased and the white blood cells and neutrophils in the blood routine may be decreased, only need to give symptomatic treatment, or can be taken orally to clear away heat and detoxification of traditional Chinese medicines, such as PuDiLan, compound fritillaries, etc., and the viral infection will be cured by itself after a certain period of time.