Diarrhea 101: Time To Talk About Something We Don't Usually Talk About

Diarrhea isn't something we usually discuss in public. But as the second leading cause of death for children younger than 5, it's a topic global health advocates want more people to talk openly about.

Worldwide, there are nearly 1.7 billion cases of diarrhea each year. The disease caused an estimated 1.5 million deaths in 2012, according to the latest data from the World Health Organization. But it's both preventable and treatable — if more people understood the underlying causes.

What is diarrhea? Three or more loose or watery bowel movements within a day. Some episodes may be triggered by food sensitivities or an intestinal disease. But the most common source is an intestinal infection. In developing countries, the main culprits are any one of four pathogens: E. coli, shigella, cryptosporidium and rotavirus. They all spread through feces-contaminated food and water, and they cause the intestines to secrete excessive fluid. When the body fails to absorb that fluid, it passes right through the guts and gets flushed out along with vital nutrients. Accompanying symptoms can include fever, abdominal pain, vomiting and severe dehydration.

How is it deadly? Mild diarrhea is no more than an inconvenience for many, but moderate to severe symptoms can lead to death from dehydration if lost fluids and nutrients aren't replaced.

Who are the most vulnerable? Those with a weak immune system, like HIV patients and the elderly. Most vulnerable are young children, whose immune systems aren't fully developed. In fact, 2015 data from UNICEF shows that diarrhea kills 526,000 children under 5 every year. A 2013 study estimates that the risk of death is especially high in the first two years of life.

Where is it most prevalent? Everyone gets diarrhea from time to time, but most at risk are the roughly 2.5 billion people living without access to toilets and the 780 million lacking clean drinking water. More than half of childhood diarrhea cases occur in Southeast Asia and sub-Saharan Africa, where many people still defecate in public, often in open spaces, behind bushes or near the water supply. India has the highest number of diarrhea-related deaths among children under 5: over 130,000 child deaths in 2013.

A vicious cycle: Even if a child survives multiple bouts, studies show that the constant mild infections damage the digestive system, making it hard for the body to absorb nutrients needed for physical and cognitive development. What results is a vicious cycle in which diarrhea leads to malnutrition, which further weakens the child's underdeveloped immune system and increases susceptibility to future infections.

What vaccines or treatments are out there? Nearly a third of severe diarrhea cases are preventable, and vaccines against the rotavirus — the most common source of diarrhea among children — are available through national immunization programs in at least 80 countries mostly in Africa and Latin America. A hundred more countries offer the vaccine through the private market. But they're still hard to come by and too expensive to provide in many low-income countries. For treating diarrhea, UNICEF and WHO recommends water mixed with a special solution of salt and sugar, along with zinc supplements, yet only 39 percent of children get that treatment.

No silver bullet: Vaccines and treatments are only part of the solution. Diarrhea will persist as long as people lack clean water, adequate sanitation and refrigeration to prevent bacteria from growing on food. In an effort to end child deaths from diarrhea by 2025, WHO and UNICEF laid out an action plan in 2013 to target those issues and involve local governments. There are also campaigns to stop open defecation, promote hand-washing with soap and encourage breastfeeding to reduce infant's exposure to food-borne bacteria. Yet a study suggests that between 1985 and 2008, there was a drop in funding for the fight against diarrheal disease.

But there are signs of hope. Over the last 15 years, overall child mortality has fallen by 4 million to 5.9 million, in part due to the reduction of deaths related to diseases like pneumonia — the leading cause of child mortality —malaria and diarrhea. But researchers behind the finding warn that the world still has a lot to do. Local and national governments alike will have to invest in water and sanitation efforts. Sometimes, though, reducing the risk of diarrhea is as simple as teaching children to wash their hands.

Our sources: Louise Maule and Therese Dooley, sanitation and hygiene specialists at UNICEF.