I would recommend that you return to the doctor and request blood work including a complete blood count. It would be helpful to know at this point if you are dealing with something that is viral or bacterial. Usually with a viral infection the white blood cell count would be normal. But with a bacterial infection, it would be elevated. If she does have a bacterial infection then she would need another antibiotic as the ones that she has taken have not adequately killed of all the bacteria. But if it is viral, then an antibiotic will not help. The blood work will also show how her internal organs are functioning such as kidney, liver, etc. as well as her immune system. If she has not been checked for mono I would also advise that the doc tests for that as well. Blood work can tell a lot about one's health so I think you should get that done.
Sometimes kids, especially teens with all the work they have to do, have a rough year with illness. Encourage your daughter to eat well and get to bed at a decent hour. A good multivitamin would also help. Try to have her talk about any stress she may be experiencing. Make sure she has some down time in addition to all of her activities. All of this will help boost her immune system.
It would also help to educate her on how a person gets sick. Most often the virus or bacteria are on one's hands and are let into the body via the mouth, nose or eyes. So, in addition to frequent hand washing, simply not touching your face at all is a good habit to learn. It's hard to get used to this but well worth the effort!
Having gone through a bad bronchitis I would expect her to not feel herself for a few weeks while she gets her strength back. Sometimes after an illness one does continue to run a low grade fever in the evenings but usually only for a week or so. That's why I think the next step you should take is getting the blood work.
If you have further questions, do not hesitate to ask.
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