Unfortunately, after publication of this article [1] it was noticed that the copyright statement is incorrect. The corrected copyright statement can be seen below:

© 2016 World Health Organization; licensee BioMed Central. This is an open access article distributed under the terms of the Creative Commons Attribution IGO License (http://creativecommons.org/licenses/by/3.0/igo/legalcode), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In any reproduction of this article there should not be any suggestion that WHO or this article endorse any specific organisation or products. The use of the WHO logo is not permitted.

This notice should be preserved along with the article's original URL