There are different causes of fever ranging from simple dehydration to different kinds of infections. The fever is just a sign that something is wrong hence the need to carry out laboratory tests to know the exact cause. You need to take the child to the hospital for an evaluation by a paediatrician.

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As for the temperature, kindly note that normal body temperature using a digital thermometer is between 36.5°c - 37.5°c, anything above is fever. You can tepid sponge