A systematic review  of 29 studies found “little to no effect from sanitation interventions” on “faecal-oral transmission of enteric and other pathogens”. The transmission pathways reviewed included “faecal pathogens or indicator bacteria in drinking water, hand contamination, sentinel toys, food, household and latrine surfaces and soil, as well as flies and observations of human faeces”.
There was some evidence showing the association of sanitation “with reductions in flies and a small effect on observations of faeces”. There was also evidence showing “an inverse relationship between the distance of a water supply from a latrine and level of faecal contamination of such water supply”.
The authors of the review conclude that current sanitation efforts in low-income countries are ineffective and unable to prevent contamination along well-known pathways. This may be because “interventions often fail to achieve universal coverage or use”, which is the subject of another systematic review .
As expected from researchers, they are also recommend that more rigorous studies are required to investigate the impact of sanitation interventions on multiple transmission pathways.
Unfortunately this important study is not available as an open access article.
 Sclar GD, Penakalapati G, Amato HK, Garn JV, Alexander K, Freeman MC, Clasen T. Assessing the impact of sanitation on indicators of fecal exposure along principal transmission pathways : a systematic review. International Journal of Hygiene and Environmental Health. 2016 Oct 1.DOI:10.1016/j.ijheh.2016.09.021
 Garn, J.V., Sclar, G.D., Freeman, M.C., Alexander, K.T., Penakalapati, G., Brooks, P.,Rehfuess, E.A., Clasen, T.F. The impact of sanitation interventions on latrine coverage and latrine use : a systematic review and meta-analysis. International Journal of Hygiene and Environmental Health. 2016 Oct 11.DOI: 10.1016/j.ijheh.2016.10.001