First thing that came into my mind when I read '6 months' was TB.

In the early days of my relationship with her mother, my stepdaughter (then living in deepest province) had a persistent cough which was diagnosed by the local doctor as 'suspected TB'. 6 months medication given. She would have been between two years and three years of age.

I'm not a doctor though... but always aware of such a possibility because my own mother contracted TB of the lungs when we were living in Malaya back in the 1950s and spent almost a year in hospital.

Us kids were closely monitored from then on, but in the end were unaffected.