It's hard to believe that in this modern age, there are still children who don't know where their next meal will come from. Or if it will come at all. Sadly, those kids are just as likely to live down the street as they are to live on the other side of the world.

KidsHealth.org recently compiled a list of the five most critical issues affecting the world's children, and poverty topped the list.

“Huge progress has been made in so many critical areas involving children’s health. Yet there is still important work to be done that doesn’t involve expensive new drugs or surgical procedures,” said Neil Izenberg, KidsHealth founder and editor. “Instead, it’s about the basics that most of us take for granted."

Here are the top five issues that affect the world's children:

1. Poverty: Almost half the world’s population lives in poverty. And 1.4 billion people live in extreme poverty, earning less than $1.25 a day. In developing countries, poverty means starvation, disease, squalid living conditions, unclean water and poor sanitation, limited or no access to education and medical care, and high crime rates. And it’s children who suffer the most. According to UNICEF, 22,000 children die each day because of poverty-related causes. Almost 30 percent of all children in developing countries are thought to be underweight or have stunted growth. This perpetuates the cycle of poverty, as these kids are less likely later to be able to earn a living wage to support themselves and their families.

Want to help? Donate or volunteer for UNICEF (The United Nations Children's Fund). As little as 50 cents a day can make a big difference in the life of a child.

2. Clean water: In most parts of the world, we take clean running water for granted. So it’s shocking to learn that 780 million people lack clean water and 2.5 million people don’t have access to a toilet. UNICEF reports that more than 5,000 children under age 5 die each day because of diarrheal diseases, often contracted through contaminated drinking water or no access to sanitation facilities, like bathrooms with flushable toilets. In developing countries, the task of collecting water usually falls to women and children, and that means hours-long walks from the home to collect water several times a day. This burden means the adults are not working at a paying job and the kids are not in school. Yet it could be an easy problem to fix. The World Health Organization estimates that it would cost $11.3 billion per year for global clean water and sanitation – in comparison, Americans spend about $450 billion each year to celebrate Christmas.

Want to help? Donate to Water.org, the nonprofit organization with the motto, "Safe water & the dignity of a toilet for all, in our lifetime."

3. Education for girls: While primary school enrollment in developing countries has risen to 90 percent, worldwide, 57 million children are not enrolled in school. The link to poverty is clear: Girls who receive little or no education face limited job prospects, putting them at an increased risk of trafficking and sexual exploitation. They’re also more likely than educated girls to contract HIV/AIDS. Educated girls are better able to find good jobs, keeping themselves and their own children out of poverty.

Want to help? Donate to the Global Education Fund, a nonprofit working to educate all kids. Families can donate, spread the word, start a fundraiser, or host an event to help raise needed funds.

4. Wiping out polio: Since the polio vaccine was introduced in 1955, worldwide cases plummeted and the disease was declared eliminated in the Unites States in 1979. Global immunization was so successful that polio was poised to join smallpox as the only infectious diseases to have been eradicated. But in three countries — Afghanistan, Nigeria and Pakistan — polio has never been wiped out, and cases of polio have been reported in Syria. Polio in faraway countries might not seem like a global concern, but as long as polio is present anywhere, outbreaks are still a risk. In fact, health experts warn that Syrian refugees could unwittingly carry the virus to parts of Europe. Until the disease is finally wiped out, it is a threat to all.

Want to help? Give to End Polio Now: Rotary International, UNICEF, the World Health Organization (WHO), the Centers for Disease Control and Prevention (CDC), and the Bill & Melinda Gates Foundation, all organizations at the forefront of the global initiative to eradicate polio.

5. Infant mortality : The joy of giving birth is usually accompanied by a sense of wonder while watching a tiny, fragile creature take those first breaths. Luckily, for most new mothers, skilled medical attendants are on hand to make sure that all goes well during and just after delivery. Yet each year almost 3 million babies die within the first month of life, mostly in low- and middle-income countries where nearly half of all mothers and newborns do not have medical care. Many of these deaths can be prevented through simple, affordable interventions that can be used in home births.

Want to help? Donate to Every Mother Counts, the nonprofit founded by supermodel Christy Turlington Burns that aims to improve the health of mothers and babies in the world's poorest places.