Broadly speaking, we can combine the water-related diseases in different categories: The one due to water polluted by human waste :

• diarrhea: 6 000 deaths / day;
• cholera;
• hepatitis;
• typhoid fever and paratyphoid;
• polio.

• fluorosis;
• arsenic;
• those due to nitrates;
• those due to fertilizers used in intensive agriculture.

• those due to Platyhelminthes (flatworms);
• those due to némathelminthes (round worms);
• bilharzia (which affects 200 million people).

• Malaria;
• dengue.

• trachoma;
• water stress.

For further informations, you can check the WHO : which describes various water-related diseases. Thus, in many parts of the world, diseases related to wetlands represent a threat to human health and the most frequently found are:

• malaria, spread by mosquitoes breeding in the wetland;
• diarrhea (including cholera) which development is promoted by sewage. In Africa, Asia and parts of the Americas, other diseases represent a major morbidity (mainly affected are children under five years), including schistosomiasis, Japanese encephalitis, filariasis, onchocerciasis, etc..

As an example, here is the geographic distribution of three water-related diseases: malaria, dengue and Japanese encephalitis.