1. Transmission Pathways: Waterborne Disease
January 26th, 2010

2. Categories of disease spread by water
Diseases contracted by ingestion of contaminated water
Often diarrheal diseases
Bacterial, viral, and parasitic diseases
Cholera, norovirus, Cryptosporidium
The largest burden of these diseases is in countries that lack water infrastructure
But they are NOT gone even in countries that have infrastructure

3. Categories of disease spread by water
Diseases spread by contact with contaminated water
Bathing, wading
Parasitic diseases where pathogen lives naturally in the water
Schistosomiasis
Leptospirosis

4. Categories of disease spread by water
Diseases spread by contact with contaminated water
Recreational waters
Example: Cryptosporidium from a spray park
Gastroenteritis from a waterpark

5. Transmission cycles in water
The fecal-oral route
Exactly what it sounds like!
Contamination of drinking water sources by human or animal fecal waste
Routes involving vectors
Organisms live naturally in the water; they are part of the ecosystem

6. Sources of Waterborne Disease
Excreta from humans and animals
Human
Shellfish
Crops
Aerosols
Oceans and
Estuaries
Rivers and
Lakes
Irrigation
Solid Waste
Landfills
Sewage
Land
Runoff
Recreation
Water
Supply
Groundwater

7. Surface Water Lakes, streams, rivers
Vulnerable to many different kinds of contamination
Direct contamination by human and animal fecal waste
Animals in and around water
Sewage disposal
Accidental sewage spills and overflows
Runoff
Stormwater
Agricultural

8. Groundwater
May be safer than surface water in some cases, but still vulnerable to contamination
Runoff into unprotected wells
High water tables can become contaminated
Transport of microbes into wells
Failing septic systems
Latrines
Chemical contamination

9. Water contamination Inadequate disposal of human feces
Partial but inadequate treatment of human fecal waste
Use of natural waterways and bodies of water as sites of sewage disposal
Example: the Mekong River

10. Water contamination and waterborne disease
Many times, a confluence of events
Contamination of source water
Lack of treatment barriers
Many people in the US drink untreated well water
Inadequate treatment barriers
Small community water systems may have trouble treating water adequately
Even large, sophisticated treatment plants can go wrong
Example: Milwaukee Cryptosporidium outbreak

11. Control of Waterborne Disease
Drinking water
Multi-barrier approach to treatment
Filters
Disinfectants

12. Control of Waterborne Disease
Water contact diseases
Breaking the chain of transmission
Getting rid of vectors
Treating infected people
Often very difficult to do
Preventing water contamination
Controlling runoff, sewer overflow, and other sources