Diarrhea

Diarrhea (DIE-uh-REE-uh), also spelled diarrhoea, happens when the body makes more watery feces than normal. Diarrhea can occur in humans as well as most other mammals.
Causes
Diarrhea is not a disease. But it may be a symptom of a disease. The most common causes of diarrhea are:
Viruses, like Norovirus (the most common cause of viral gastroenteritis--"stomach flu"--in humans)
Bacteria, like E. coli or C. diff
Some medicines, especially antibiotics
Food poisoning
Lactose intolerance
Artificial sweeteners, like sorbitol and mannitol, which are in many sugar-free food products like sugarless gum
Other problems with the intestines, like Crohn's disease and irritable bowel syndrome
Child death
In developing nations, diarrheal diseases are the second most common cause of death in children under age 5. Every year in the world, diarrhea kills around 760,000 children under age 5.
In developing countries, diarrhea is also one of the most common causes of malnutrition in children under age 5.
When children die from diarrhea, the cause is often dehydration (losing too much water from the body). Because diarrhea is watery, it takes away a lot of the water. It also takes away electrolytes--important salts that the body needs to survive. Dehydration is extra dangerous for small children because they have less water in their bodies to begin with. This means they cannot lose as much water as adults before they start to have serious health problems.
Causes
In developing countries, diarrhea is usually caused by an infection in the intestines. These infections can be caused by bacteria, viruses, or parasites. These infections spread easily in some developing countries because of the following reasons:
Unsafe drinking water. Bacteria, viruses, and parasites often get into the water, which people then have to drink. Anyone who drinks the water can then get an infection that causes diarrhea.
Sanitation, with clean toilets, is often not available. This makes it easier for infections to spread.
Clean water and soap for washing hands are often not available, either. If people cannot wash their hands, bacteria, viruses, or parasites can stay on their hands. These microbes can then enter the mouth or get spread to other people with handshaking.
Preventing child deaths
Child deaths from diarrhea can be prevented in different ways.
Re-hydration
When a child is sick with diarrhea, the best way to keep them from dying is to rehydrate them (give them the water and electrolytes (salts) they are losing by having diarrhea). If the child can go to a clinic or hospital, this can be done by giving water and salts intravenously (through a needle placed into a vein).
If the child cannot go to a clinic or hospital, oral rehydration solution can be used. ("Oral" means "given by mouth"; a "solution" is a mixture.) Oral rehydration solution is a mixture of the most important things the body loses when it is dehydrated. These things are clean water, salt, and sugar. Some oral rehydration solutions have extra electrolytes, like potassium, in them also.
Some oral rehydration solutions come in packets and just need to be mixed with clean water. Oral rehydration solution can also be made at home. If the water in the area is not safe, it can be boiled to make it safe. (Boiling the water will kill any bacteria, viruses, or parasites in the water.) Salt and sugar are then mixed into the water. Drinking this mixture, after the water cools, will re-hydrate the child, if he drinks enough. Adding a banana or orange juice can add potassium to the mixture.
Breast milk will also re-hydrate a child with diarrhea.