Impact are obviously different depending on the disease. There are mainly three kind of diseases which touch Nigeria: chronic diseases, tropical diseases and diseases which steam from poor sanitation.

• Chronic diseases: Chronic diseases create large adverse – and underappreciated – economic effects on families, communities and countries. In 2014 alone, it is estimated that Nigeria will lose 400 million dollars[1] in national income from premature deaths due to heart disease, stroke and diabetes (reported in international dollars to account for differences in purchasing power between countries). These losses are projected to continue to increase: cumulatively, Nigeria stands to lose 8 billion dollars over the next 10 years from premature deaths due to heart disease, stroke and diabetes. WHO estimates that a 2% annual reduction in chronic disease death rates in Nigeria would result in an economic gain of 500 million dollars for the country over the next 10 years.
• Tropical diseases: Urinary schistosomiasis is the most prevalent of the endemic tropical diseases: 48% of the population is afflicted in the study area. The socio-economic, environmental and health-seeking behavioural characteristics of the population are conducive to the spread of urinary schistosomiasis. The attitudes considered include knowledge of what causes the disease and how to control it, attitude toward the disease, care of oneself, hygiene and sanitation. The effect of such social variables as stigmatisation, and environmental variables such as water source is also considered to calculate the effect of the tropical disease. Losses from work attributed to urinary schistosomiasis are high. Average values of key socio-economic variables-labour flow for land clearing, farm size and cash income-computed for farm families with high urinary schistosomiasis intensity in the sample are 1085 h, 1.4 ha and N 1,432 (US dollars 65) respectively. The corresponding figures for farm families free from the disease are significantly higher: 1325 h, 1.9 ha and N 3,759 (US dollars 171), respectively[2].
• Diseases from poor sanitation: Poor sanitation costs Nigeria 455 billion Naira each year, equivalent to US$3 billion[3] according to a desk study carried out by the Water and Sanitation Program (WSP). This sum is the equivalent of US$20 per person in Nigeria per year or 1.3% of the national GDP: 70 million Nigerians use unsanitary or shared latrines, 32 million have no latrine at all and defecate in the open, the poorest quintile is 10 times more likely to practice open defection than the richest. Open defecation costs Nigeria US$1 billion per year – yet eliminating the practice would require less than 6.5 million latrines to be built and used.
• Epidemic outbreak cost: Fecal contamination of the environment is the root cause of an annual average of 5,400 cases of cholera affecting Nigeria. The cost of the necessary WASH response is estimated to be US$3.5 million[4] each year. However, the economic implications of a cholera outbreak go beyond the immediate health system response – there are also costs related to productivity loss and premature death, diverting expenditures from other essential items and losses in trade and tourism revenue.

[1] World Health organization : chronic diseases report in Nigeria
[2] The socio-economic effects of tropical diseases in Nigeria. Umeh JC  Amali O, Umeh EU.
[3] Water and sanitation program : Nigeria
[4] Water and sanitation program : Nigeria report

Economic Lost Due to Poor Sanitation In Nigeria 

source: WHO