Worldwide number of new TB cases is higher than any other time in history

From the 2011 Lancet review:

The worldwide number of new TB cases is more than 9 million - higher than at any other time in history.



22 low-income and middle-income countries account for more than 80% of the active cases in the world.



Due to the devastating effect of HIV on susceptibility to TB, sub-Saharan Africa has been disproportionately affected and accounts for 4 of every 5 cases of HIV-associated tuberculosis.



Management problems include:



- In highly endemic areas, TB diagnosis continues to rely on century-old sputum microscopy



- No vaccine with adequate effectiveness (although BCG works to some extent). According to a recent report, BCG vaccination not only protects against tuberculosis but the number needed to treat (NNT) is 11.



- TB treatment regimens are protracted and have a risk of toxic effects



- Increasing rates of drug-resistant tuberculosis in eastern Europe, Asia, and sub-Saharan Africa

Promising progress includes improved tuberculosis diagnostics with biomarkers of disease activity. New and improved drugs, biomarkers, and vaccines need to be developed.

Diagnosing tuberculosis with cytokines IL-15, IL-10 and MCP-1, in addition to interferon-gamma

A pattern of two cytokines, called MCP-1 and IL-15, was reasonably good at differentiating between persons sick with TB and persons infected but not sick.

Monocyte chemotactic protein-1 (MCP-1) is a small cytokine belonging to the CC chemokine family. According to the new nomenclature, MCP-1 is called chemokine (C-C motif) ligand 2 (CCL2).

A third cytokine called IP-10 also showed promise at differentiating between people who are infected and those who are not.

Interferon gamma-induced protein 10 kDa (IP-10) is also known as C-X-C motif chemokine 10 (CXCL10). It belongs to the CXC chemokine family.

These 3 cytokines could form the basis of a new test to quickly detect whether tuberculosis is dormant or active and infectious.

52 chemokines from 4 families have been described. They interact with 20 receptors (click here for a larger image).

References:



Tuberculosis. Stephen D Lawn MRCP, Prof Alimuddin I Zumla FRCP. The Lancet, Volume 378, Issue 9785, Pages 57 - 72, 2 July 2011.

Immune system could be used to test for TB. Reuters.

Immunology Made Simple: "What are These People Talking About?"

Cytokines

Xpert MTB/RIF is a rapid diagnostic test for tuberculosis with high sensitivity (90%) and specificity (99%). Lancet, 2011.

Image source: PPD, CDC, public domain.

Comments from Twitter:

@sdietrich17: How discouraging. We just keep going backwards with so many infectious diseases...