Human infectious diseases are among the most serious effects of water pollution,
especially in developing countries, where sanitation may be inadequate or
non-existent. Waterborne diseases occur when parasites or other disease-causing microorganisms are transmitted via contaminated water, particularly water
contaminated by pathogens originating from excreta. These include typhoid,
intestinal parasites, and most of the enteric and diarrheal diseases caused
by bacteria, parasites, and viruses. Among the most serious parasitic diseases
are amoebiasis, giardiasis, ascariasis, and hookworm.

Developed countries are not immune to the problem of infectious waterborne
diseases. In 1993, high cryptosporidium levels in Milwaukee’s drinking water
supply sickened more than 400,000 residents. That was an unusually extreme
case, but transmission of disease agents such as bacteria and cysts via
contaminated but poorly treated municipal water is more common than it
should be. Every year, seven million Americans are sickened by contaminated
water. This is only partly due to drinking water—contamination of recreational
water (such as beach water) is also a problem.

Every year there are thousands of beach closings in the US, and outdated
monitoring methods may in some cases leave beachgoers vulnerable to a
range of illnesses. Polluted beach water can cause rashes, ear aches, pink eye,
respiratory infections, hepatitis, encephalitis, gastroenteritis, diarrhea, vomiting,
and stomach aches. Hey, that’s no day at the beach!

WATER-RELATED DISEASES NOT RELATED TO WATER POLLUTION

Water-based diseases are somewhat similar to water-borne diseases but are not
typically an effect of water pollution. They come from infectious agents that naturally
spend part of their life cycles in water. Humans can become infected when they
drink or come in contact with the water that serves as home to these organisms .
One of the most widespread examples in this category is schistosomiasis, which
currently infects 200 million people in 70 countries. Similarly, diseases like malaria
and dengue fever are spread by insects that breed or feed near water.

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