Reactivation or reinfection - or what?

A large study of 3,483 adults from 837 households from Cape Town, South Africa found that

The prevalence of bacteriologically confirmed TB in our study was high, and the proportion of patients that had >1 previous episode of TB was substantial. 

This means that

persons with previously treated TB are likely to contribute to transmission of Mycobacterium tuberculosis

The reason for the continued presence of TB could be improper treatment however

recent studies using DNA fingerprinting showed that a large proportion of recurrent TB in our study area is caused by exogenous reinfection rather than reactivation 

The presence of HIV may not be a critical factor

we believe that the prevalence rate for HIV in the study area is less than the rate of 12.4% in women attending public antenatal clinics in Cape Town in 2002

and similarly with the presence of drug resistant strains

Drug-resistant TB is probably not the driving force behind the high prevalence of TB in the 2 study communities

The only real conclusion from this is that current treatment strategies are unsuccessful. The WHO have found that treating only active TB is insufficient, you must treat both active and latent TB

and this is supported by other studies, such as this one from Vietnam

the trend in TB notification among young adults reflects increased rates of progression from infection to disease and/or increased transmission within this age group, rather than increased transmission in the population at large.

If IGRAs, by eliminating TST false positives, demonstrate that the prevalence of latent TB is less than previously thought the obvious conclusion is that the rate of progression to an active state is higher than previously thought.

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