Thank you for your query,
The test done to detect typhiod is Widal test
and usually it will be positive in cases of typhoid
after 5 to 7 days of fever.
Typhoid is not diagnosed with ultrasound
abdomen, but can be suspected if ultrasound is showing any enlargement of liver and spleen.
Continue the medication as advised by your Pediatrician
Typhid usually takes 10 days to 2 weeks for recovery.
Hope I have answered your query.