Fever for one month with 1 week investigation is defined as 'fever of unknown origin'. All first line investigations has been done in your child except tuberculin test for tuberculosis
, widal test
for typhoid and blood culture
If all first line investigations are normal then get second line investigations like HIV ELISA, complement levels, brucella
serology, test for infectious mononucleosis
I will suggest you to consult your doctor and get all these investigation done to reach a diagnosis and then management accordingly.
In most of the cases a diagnosis is made. Sometimes it may not be possible to reach a diagnosis even after thorough investigation.
Empirical broad spectrum antibiotic is used for treatment of the fever. Some cases of FUO resolve over a period of time.