The Missing Millions…

This part of our analysis of the 2014 Global TB Report relates to the tricky subject of rates of incidence, prevalence and notification. Before getting into a little necessary detail, we’d first like to review what these terms mean in respect of Global TB Reports:

The incidence is the estimated number of cases who are believed to be newly infected with the active disease in a given year (in the case of the 2014 Report during 2013)

The prevalence is the estimated number of cases who are actually believed to have the active disease during any given year – with a slow disease like TB (that can last for years if untreated and which has long periods of treatment) this will be different to the incidence rate and will under normal circumstances be expected to be higher.

The notification is the number of cases which have actually been diagnosed in national TB programmes and  notified to the WHO in the same period (i.e. unlike the other two measures, this number is not an estimation).

The gap between the total estimated number of prevalent cases and the total known notifications can then be usefully calculated. This is an important estimated measurement in combating any infectious disease – because it reflects the number of infectious cases that are figured to be out there who either are getting no treatment at all or who are receiving treatment that is unapproved, thus remaining potentially able to infect others and sustain the pandemic.

The current official quotas of these categories are roughly as follows:

            Incidence                   9 million

            Prevalence              12 million

            Notification               6 million

With TB globally (and here we’re not talking about drug-resistant disease here, we’re talking about the whole general global pandemic TB today) these rates have been remaining pretty much the same for the past few years, and everyone accepts that efforts need to be scaled up dramatically if further progress is to be made. 

But that’s not all. The number and proportion of the notifications in particular offer a pretty useful picture of what progress is being made in finding and treating those missing cases. If you can find and successfully treat pretty much all of the estimated infectious cases, then the days of any infectious disease become essentially numbered.

Over the last few years, however, this critical number of notified cases has been sticking at around 6 million.  It surely is a lot of potentially infectious cases on the loose, but what's just as important is this fact that it’s not really been moving. You can see from the list above, however, that there are estimated to be roughly half as many  (i.e. 3 million) of the incident cases who are still getting infected year on year and who aren’t being notified at all; but more worryingly still there is overall practically the same total amount as these notified cases (i.e. 6 million) out there who are “prevalent” and therefore living with the disease in a potentially infectious state.

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A full 21 years into an officially declared global emergency getting to grips with just 50% of a pandemic is anything but encouraging and frankly it's not much of an achievement whatever may be being said about hitting targets. Given that even approved TB treatment doesn’t always have a successful outcome, it suggests that less than half of the estimated prevalent cases are being cured - and TB, we should remind ourselves, is considered to be a curable disease if it's not drug-resistant. Is this remotely acceptable as a proper global response 21 years down the track?

Back in 2013 the WHO’s call to arms was to “find the missing 3 million!”.  A year later and it looks like not that many of them can have been found. But shouldn’t the question anyway really have been “find the missing 6 million”, or would that have been a step too far?

Any which way, the current death toll from TB (around one and a half million, but probably a lot more) looks to have promoted this old infectious enemy once again to being the most lethal infectious agent loose on our planet – and, if this is true, then surely correspondingly far more massive efforts should  already be being made to redress this. Given that these notification numbers are proving so sticky it clearly tells us that this can’t yet be happening: nowhere near enough effort – particularly political effort - is yet being made…

What we are now quite sure of is this: that, whatever PR story may being spun concerning ‘progress’ or hitting any of the targets that were set for 2015, far too little progress has yet been made and far, far too many are still dying from TB each year. 

It's undeniable that TB is a complex disease with no simple solutions, but nevertteless something needs to be done about it.

For the other four analytical discussions of the 2014 Report:

     MDR-TB - two more questions