As Vice President of Field Programs at PATH, I appreciate efforts like World Water Day that call for universal access to the solutions that are the foundation to the health and well-being of communities. I appreciate these efforts both as a public health expert and as a native Nigerian who has seen firsthand the burden of disease in Africa, where diarrhea is now the leading killer of children under five.

I grew up in Nigeria and my family was fortunate enough to have safe drinking water and a toilet. Millions in my country did not, however, and many still don't today. Later in my life, when I became a doctor practicing in Ilorin, I saw many children who were far too small for their age. I remember one mother in particular who visited my clinic several times with her tiny child, who was severely dehydrated. It wasn't difficult for me to imagine why he was repeatedly ill. Lack of access to water, sanitation, and hygiene (WASH) is devastating in its own right, but when other family members are ill with diseases like malaria or tuberculosis and waste is not disposed of properly, the dangers are compounded. In these environments, it's no surprise that diarrheal diseases are perpetual and unforgiving, especially among vulnerable children and those who are already ill.

Those of us living in industrialized nations can easily forget the extent to which we rely on safe drinking water and sanitation to stay healthy and to prevent the spread of disease. In fact, no innovation in the past 200 years has done more to save lives and improve health than sanitation. And anyone who has suffered with a water-borne illness knows how difficult it would be to be productive in that condition. In nations like the U.S. where diarrhea has become a mere inconvenience, too many are unaware that diarrhea is still the second leading killer of children globally. When it doesn't kill, a long cycle of dehydration and malnutrition takes its toll, and both physical and cognitive stunting are often sad long-term consequences.

Worldwide, millions lack access to safe drinking water and billions lack a latrine: a major contributor to the 1.5 million children who die of diarrheal diseases every year, a security risk for women who have to journey long distances for water and for privacy, and a deterrent to girls' school attendance. The cost of continuing to ignore this crisis is high. Fortunately, so is the opportunity for effective solutions. To defeat diarrheal disease, we need an integrated prevention and treatment approach, and WASH is essential to that equation. Over half of the hospital beds in low income countries are filled with patients suffering with water-borne diseases. Imagine the impact that simple access to WASH could have in those settings. Imagine the impact it could have had on that mother who repeatedly brought her child to see me at the clinic. Chances are, she never would have needed to come. A cup of safe drinking water and a latrine are so much more than health solutions; they are hope for mothers everywhere, all of whom want the same things for their children.

World Water Day is a great opportunity to celebrate success and to renew our commitment moving forward. The recent achievement of the safe water MDG target ahead of schedule is worthy of celebration and shows us what's possible, but the lagging behind of the sanitation MDG target, not to mention the many families who still lack access to safe drinking water, is a sobering reminder that we can't stop here.

We all have a role to play. Just as WASH solutions are simple but powerful, so is our request to advocates on World Water Day: to lend your voice to the cause. Visit waterday.org to sign up your Facebook or Twitter profile and share messages about the incredible impact of WASH. Your voice can help save lives. Join the movement.

-- Ayo Ajayi is Vice President of Field Programs at PATH