Diarrhea is responsible for 9 percent of all deaths among children under age 5 around the world, making it their leading cause of death, according to UNICEF. The condition is characterized by passing three or more loose or liquid stools each day, and although proper sanitation is estimated to have reduced diarrheal risk in young kids by 36 percent, new research published in PLOS Medicine suggests sharing a sanitation facility can actually increase this risk.

The viruses, bacteria, and parasites that cause diarrhea often come from contaminated food or drinking water, or through poor hygiene like failing to wash one’s hands after using the toilet. Inadequate sanitation and the unsafe disposal of human waste also play roles in transmission. The current study, conducted by Kelly K. Baker of the University of Iowa College of Public Health, found another potential risk: sharing a sanitation facility, such as a toilet or latrine, with just one to two other households increases risk of moderate-to-severe diarrhea in young children. Based on these findings, researchers suggested that access to private sanitation facilities should remain a global health priority.

The study was meant to observe instances of pediatric diarrhea in children under 5 years old living in seven regions in Africa and South Asia. Researchers compared 8,592 children diagnosed with clinically and laboratory-confirmed diarrhea to 12,390 asymptomatic children in order to unveil any associations between household sanitation and risk of diarrhea.

The data revealed that, compared to those with a private household sanitation facility, children living with families that shared facilities with one or two other households had an increased risk of diarrhea in Nyanza Province, Kenya; Bamako, Mali, and Karachi, Pakistan. Sharing a facility with three or more households was associated with further increased diarrheal risk. However, sharing a sanitation facility was not found to be associated with increased risk at the sites located in Basse, The Gambia, Mirzapur, Bangladesh, and Kolkata, India.

“While shared sanitation may not be a risk factor in some communities, our study demonstrates that many children around the world do face risks from sharing sanitation facilities,” the researchers wrote.

Because the study is observational, it does not prove a causal relationship between sharing sanitation facilities and an increased diarrhea risk. The correlation between the two could be due to the fact that families with private sanitation facilities also prioritize safe hygiene practices.

“The reduced risk of diarrhea in these households might then be the result of everyone washing their hands after using the toilet rather than the result of having a private latrine,” researchers wrote.

Nevertheless, the study provides compelling evidence about shared sanitation and diarrhea risk. The relationship between “sanitation infrastructure, human behavior, and enteric disease risk in young children are complex” and not fully understood, the researchers wrote, adding that further insight will better help them understand the risks these facilities pose.

Source: Baker K, O’Reilly C, Levine M, et al. Sanitation and Hygiene-Specific Risk Factors for Moderate-to-Severe Diarrhea in Young Children in the Global Enteric Multicenter Study, 2007–2011: Case-Control Study. Plos Medicine. 2016.