# 6071
With practically any disease you’d care to mention the number of cases that we see, and are counted, generally represent only a small subset of the total.
As the chart from the CDC below indicates, public health officials are usually only aware of the `tip of the disease pyramid’.
Many people suffering an illness do not become sick enough to seek medical care (or may live in an area where such care, or testing is unavailable). Those that see a doctor may not be properly diagnosed. And those that are diagnosed may not be reported to the health department.
When the World Health Organization announced the detection of the 571st human H5N1 infection, or the ECDC reports that 4,200 people were infected by the E. coli O104:H4 outbreaks in Germany and France, everyone in the public health arena understood that those numbers are unlikely to include all of the cases out there.
Reporting and surveillance – even in technologically advanced regions like the United States and Europe – are simply not that good.
So when we learn – as we have this week – of a dozen cases of `totally resistant tuberculosis’ in India, it’s a pretty fair assumption that there are more cases out there, as yet undetected.
The question is: How many?
While the answer to that question remains elusive, we’ve some troubling hints today from an article that appears in the Indian Express.
The story revolves around an interview with Dr John Kenneth, Professor and Head, Infectious Diseases, St John’s Research Institute. The article can be accessed at the following link:
Johnson T A : Bangalore, Sat Jan 14 2012, 03:47 hrs
While the headline, that this new form of resistant TB `may be more widespread’ is practically a given - what is worrisome are the percentages being reported.
Dr. Kenneth states that his group has unpublished data showing that out of one hundred TB patients they had randomly selected for drug susceptibility studies, six were found to be `totally drug resistant’.
Additionally out of these 100 cases, 30 were found to be multi-drug resistant (MDR), and 13 were defined as being extensively drug resistant (XDR).
Dr. Kenneth admits that there may be some selection bias in the 100 patients selected for this study, and that all cases tested were randomly selected from among TB patients at only one treatment facility.
Until this study is published, we are lacking details on how the screening for drug resistance was done, and exactly how `totally drug resistant’ was defined. This is an issue that the ECDC brought up earlier this week, when they cautioned against the use of the term TDR-TB (see ECDC Comment On Drug Resistant TB In India).
Whether these results reflect the prevalence of resistant TB across a wider region is – for now, at least – unknowable.
For more on all of this, you can’t do better than Maryn McKenna’s coverage on her Superbug Blog. Her latest entry (which includes links to her radio interview yesterday) can be read at:
For some more background on Tuberculosis, which kills 1.7 million people each year, last March I wrote a blog titled World TB Day: March 24th.
Some of the resources I cited that day may be of interest.
(From the 2011 TB Progress Report)
The World Health Organization released a new report and a factsheet on MDR-TB & XDR-TB in advance of this yearly event on the the status of Tuberculosis around the world and the progress being made in its control.
WHO progress report 2011
While progress has been cited in the global fight against tuberculosis, the addition of a new supposedly `totally resistant’ form of TB to the mix complicates matters enormously.
Yesterday the WHO published the following notice:
13 January 2012 | Geneva | WHO's Stop TB Department has just published a briefing note with "Frequently Asked Questions" to provide information on tuberculosis that is resistant to all drugs.
In 2006, the first reports of extensively drug-resistant tuberculosis (XDR-TB), an even more severe form of drug resistant TB than multidrug-resistant TB (MDR-TB), began to appear. Within a year of the first reports of XDR-TB, isolated cases were reported in Europe that had resistance to all first-line anti-TB drugs (FLD) and second-line anti-TB drugs (SLD) that were tested. In 2009, a cohort of 15 patients in Iran was reported which were resistant to all anti-TB drugs tested. The terms “extremely drug resistant” (“XXDR-TB”) and “totally drug-resistant TB” (“TDR-TB”) were given by the respective authors reporting this group of patients. Recently, another study has been published that describes 4 patients from India with resistance to all tested drugs.
