dear user these symptoms of fainting followed by fever you mentioned refer to having underlying disease caused by bacterial infection or viral infection you need not to worry as the most common cause is viral infection and so we dont need tobe stressed and just follow these simple steps you should take antipyretics and drink multiple fluids will help then improvement will occur gradually if the cause is viral infection as it take about four days and symptoms will improve...... if symptoms persist or get worse we suggest that there is bacterial infection and antibiotic indicate now you should do ssome investigations to detect cause as widal test for typhoid ,urine culture for possibility of uti ,blood test if any other symptom you feel you should examine that with your doctor consultation as it may help alot.....antibiotic is prescribed according to these tests just now you need not to worry if you feel gradual improvement also stress and anxiety can cause these symptoms wish you happy life