Why is my wife having fever?

Q: My wife is suffering from mild fever, which ranges between 98.7°F and 99.5°F, for the last 10 days. She is 31 years old. Her tests for typhoid, malaria and TB were all negative. What can be the cause of this type of fever? Are there any tests that need to be done?

A:Fever is an increase in body temperature above the normal range of 98.4 ± 0.7°F. Normally, there is a variation between the morning and evening body temperature, which is called diurnal variation i.e. the evening temperature is usually higher than the morning temperature. The majority of short duration fevers (less than 2 weeks) are due to infectious causes, like viral infections, malaria, bacterial infections of the lungs, intestines or urinary tract. Rarely, short duration pyrexia can be due to a non-infectious cause like drug allergy or gout. A clinical examination by the doctor along with basic investigations can usually find the cause of the fever.