Half the hospital beds in developing countries are filled with people suffering from diseases caused by poor water, sanitation and hygiene.
(UNDP Human Development Report, 2006 http://hdr.undp.org/en/media/HDR06-complete.pdf  page 45)

Lack of water, sanitation and hygiene costs Sub-Saharan African countries more in lost GDP than the entire continent gets in development aid.
(Using percentage estimate from UNDP: Human Development Report, 2006)