If your baby has a sudden fever without symptoms, it may be a viral infection. Take your child to the hospital to check the blood count and C-reactive protein, and also check the throat for redness, swelling, congestion or pus. If there is inflammation in the throat and an elevation of C-reactive protein in the blood test, it is often caused by a viral infection. These toxins stimulate the body’s thermoregulatory center and cause the temperature to shift upward, resulting in fever. In addition, if there is an increase in white blood cells, accompanied by an increase in C-reactive protein, it is often caused by a bacterial infection, which, like viral infections, is also due to an upward shift in the body temperature setting point, and requires anti-inflammatory treatment with appropriate antibiotics or antiviral drugs depending on the type of infection. In addition, if the temperature of the fever is particularly high, over 38.5°C, the baby also needs to be given oral ibuprofen suspension to reduce the fever.