It has been argued that sanitation engineers have accomplished more to improve health and save lives than all the medical doctors of the past 150 years. Clean drinking water, modern sanitation facilities, and education about hand washing are absolutely key to public health. Yet 2.4 billion people — nearly one-third of the world's population — still lack modern sanitation; and 1.1 billion — one-sixth of the population — lack access to clean drinking water.
When disease-carrying bacteria in contaminated drinking water are swallowed, they multiply in the intestine and release toxins. This causes vomiting and diarrhea, leading the body to lose large amounts of fluid and salts. Four billion cases of diarrheal diseases occur around the world each year, with some two million infants and children dying, usually from dehydration. In fact, diarrheal diseases account for 18 percent of deaths among children under 5; of these deaths, 40 percent are in Africa.
Cholera, one of the most feared of these diseases, occurs when water supplies become contaminated by the marine bacterium Vibrio cholerae. In the 19th century, sailors and traders picked up the disease and carried it around the world. In 1854, English physician John Snow traced a cholera outbreak to a public well in London. While he did not know about germ theory, he had observed enough illness among users of the well that he had it shut down. By the end of the century, improved sanitation helped Europe and North America suppress the disease. Today, cholera outbreaks still occur periodically, especially in cities in the developing world with inadequate sanitation and unclean drinking water.
A major breakthrough in the treatment of diarrheal dehydration came in 1832 when it was discovered that intravenous fluids and salts could help to prevent death. In the early 1970s, scientists working in Bangladeshi refugee camps discovered that a solution of sugar, salt, and water could be administered by mouth to cholera victims to keep them hydrated. Oral-rehydration therapy, as it's called, was one of the keys to the UNICEF-led Child Survival Revolution. Mothers around the world learned how to keep their children hydrated by either preparing a homemade hydration solution, using the UNICEF oral-rehydration packets dissolved in water, or, if they could afford it, purchasing a commercial product like Pedialyte. Oral-rehydration therapy is considered one of the greatest public health breakthroughs of the 20th century, saving the lives of millions of children.
Families can help prevent illness by disposing of feces safely, by washing their hands after defecation and diaper changes, and before preparing meals and feeding children.
Diarrhea-causing bacteria are not only waterborne. Diarrheal diseases can be caused by the Shigella bacteria, found in contaminated milk and dairy products, salads, and poultry, in addition to contaminated bodies of water; by amoebic dysentery (the cause of most travelers' intestinal complaints, contracted through food or water that has been contaminated by fecal matter); by typhoid (caused by eating food or drinking water contaminated with Salmonella typhi bacteria); and by the rotavirus family of viruses, which commonly affect children.
New vaccines against rotavirus are becoming available, and if universally applied, experts say they could reduce diarrheal deaths among children by approximately a third. A "cocktail vaccine" against all causes of diarrhea remains a hope for the future.