Burden, Prevalence, and Associated Factors of Diarrhea Among Children Under Five: A Systematic Review and Meta-analysis

Every year, millions of young children around the world fall ill with a condition as simple and universal as a loose stool, yet one that carries a devastating weight in many parts of the globe. This illness, known as diarrhea, occurs when a child passes three or more loose stools in a single day, or when their stool becomes noticeably looser than usual. While often dismissed as a minor inconvenience in wealthier nations, it remains a leading cause of death for children under five in low- and middle-income countries. The danger lies not just in the illness itself, but in how easily it spreads and how it weakens a child's body. The transmission is often silent and invisible, moving through water contaminated by bacteria or viruses, food handled with unwashed hands, or soil touched by unsafe waste disposal. When a child drinks from an unsafe source or plays in an area where sanitation is poor, they are exposed to microscopic pathogens that their developing immune systems struggle to fight. Beyond the immediate sickness, repeated episodes can stunt growth and impair cognitive development, creating a cycle of poverty and poor health that is difficult to break. Understanding exactly how widespread this problem is, and what specific conditions make it worse, is the first step toward saving lives.

To map the true scale of this challenge, two researchers, Mohammed Omar Musa Mohammed and Dawit G Ayele, set out to gather and analyze a vast collection of existing studies. They did not conduct new experiments in the field; instead, they acted as synthesizers, hunting down every relevant scientific paper published between 2015 and 2025 that focused on children under five in Africa and Asia. Their goal was to move beyond isolated snapshots from single countries and create a unified picture of the situation across two massive continents. They searched through thousands of records in major scientific databases, carefully filtering out anything that did not meet strict criteria. They looked only for studies that provided clear numbers on how many children were sick and what factors were linked to that sickness. After a rigorous process of screening titles, reading full texts, and checking the quality of the data, they settled on thirty high-quality studies. These studies represented a massive pool of information, covering 17 different countries and a combined total of more than 461,000 children.

When the researchers combined the data from these thirty studies, a clear and sobering picture emerged. They found that, on average, about one in six children under the age of five in these regions experienced diarrhea during the time periods measured in the studies. This translates to a prevalence rate of roughly 16.7 percent. However, this average masked a story of deep inequality and geographic disparity. The burden of the disease was not shared equally. When the researchers looked at the data broken down by continent, they found that the situation was significantly more severe in Africa than in Asia. In African countries, the pooled rate climbed to nearly 19 percent, whereas in Asian countries, it stood at just under 11 percent. The variation between individual countries was even more striking. In some settings, such as parts of Malaysia, the rate was as low as 4.4 percent, while in specific communities in Uganda, it soared to more than 62 percent. This wide gap suggests that while the disease is a regional problem, the intensity of the crisis depends heavily on local conditions, with some communities facing a far more acute emergency than others.

The study also took a deep dive into the specific factors that push a child toward illness, identifying a consistent pattern of risk that spans across different cultures and borders. The most powerful drivers of diarrhea were found to be linked to the basic environment in which a child lives. Access to safe drinking water was a critical factor; children who relied on unimproved or unsafe water sources were at a much higher risk. Similarly, poor sanitation played a major role. When households lacked proper toilets or when child feces were not disposed of safely, the environment became contaminated, allowing germs to spread easily. The practice of handwashing, or the lack of it, was another decisive element. Caregivers who did not wash their hands before preparing food or feeding a child inadvertently facilitated the transmission of disease. These findings confirm that the disease is not just a biological event but a consequence of infrastructure and daily habits.

Beyond the physical environment, the study highlighted that social and economic factors are deeply intertwined with health outcomes. Children whose mothers had lower levels of education were more likely to suffer from diarrhea, likely because education often correlates with knowledge of hygiene and health practices. Household poverty was another significant predictor; families with fewer resources often lived in more crowded conditions with less access to clean water and healthcare. The age of the child also mattered, with those between six and twenty-three months being particularly vulnerable. This is a critical window in a child's life when they begin to crawl and explore their surroundings, putting them in contact with contaminated surfaces, while simultaneously transitioning from exclusive breastfeeding to solid foods that may be prepared under less than ideal conditions. The study reinforced that exclusive breastfeeding for the first six months of life acts as a powerful shield, protecting infants from exposure to contaminated water and food.

The researchers were careful to test the reliability of their findings, ensuring that the results were not skewed by a single outlier study or a specific type of data. They performed a series of checks to see if removing any one study would change the overall conclusion, and the results remained stable. They also examined whether the size of the studies or the year they were published influenced the numbers, finding that smaller studies tended to report slightly higher rates, a common pattern in this type of research. While the data showed a high degree of variation between the different studies—meaning the conditions in each location were unique enough to produce different results—the core message remained consistent. The high rates of diarrhea are not random; they are the predictable outcome of specific, modifiable risks. The study did not find evidence that the situation was improving or worsening over the decade they studied, suggesting that without targeted intervention, the burden remains stubbornly high.

The implications of these findings point toward a need for solutions that go beyond simple medical treatment. Because the root causes are so diverse, ranging from the quality of water to the education of mothers, the response must be equally broad. The researchers argue that tackling diarrhea requires an integrated approach that combines improvements in water and sanitation with efforts to reduce poverty and support maternal education. Promoting exclusive breastfeeding and ensuring safe disposal of waste are not just health recommendations but essential public health strategies. The data suggests that in the most affected regions, particularly in Africa, these interventions are urgent. By addressing the environmental and social conditions that allow the disease to thrive, communities can break the cycle of illness. The study concludes that while the challenge is substantial, the path forward is clear: coordinated action across multiple sectors is essential to protect the most vulnerable children and move closer to global health goals.