While I agree that private sanitation is preferable for many non-health related reasons, I am wondering a bit how a toilet shared between 2-3 households is different from one used by a larger family for example. Maybe one can make a case for toilets used by more people to be more risky, but looking at the household figure seems to confuse the issue.

In general, I suspect that this is rather a correlation and not a causation. Communities that have a lack of private toilets and are thus resorting to sharing with direct neighbors are likely to be less well off economically and also likely more un-hygienic in other aspects as well.

thankyou Dan for sharing the findings from these 2 robust and comprehensive pieces of research which both point towards a very important conclusion :

i) Sharing a sanitation facility with 1-2 other households can increase the risk of moderate-to-severe diarrhea in young children, compared to using a private facility.

ii) Evidence confirms that private sanitation often provides greater benefits than shared sanitation.

>> Interventions aimed at increasing access to private household sanitation facilities may reduce the burden of moderate-to-severe diarrhea in children.

The current issue of PLoS Medicine has an important review on sanitation and hygiene and also below is an analysis of the review by Jonny Crocker and Jamie Bartram.

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 Med, May 2016. Authors: Kelly K. Baker, Ciara E. O’Reilly, Myron M. Levine, Karen L., et al.
Full text: goo.gl/z0h9P0

Background - Diarrheal disease is the second leading cause of disease in children less than 5 y of age. Poor water, sanitation, and hygiene conditions are the primary routes of exposure and infection. Sanitation and hygiene interventions are estimated to generate a 36% and 48% reduction in diarrheal risk in young children, respectively. Little is known about whether the number of households sharing a sanitation facility affects a child's risk of diarrhea. The objective of this study was to describe sanitation and hygiene access across the Global Enteric Multicenter Study (GEMS) sites in Africa and South Asia and to assess sanitation and hygiene exposures, including shared sanitation access, as risk factors for moderate-to-severe diarrhea (MSD) in children less than 5 y of age.


Methods/Findings - The GEMS matched case-control study was conducted between December 1, 2007, and March 3, 2011, at seven sites in Basse, The Gambia; Nyanza Province, Kenya; Bamako, Mali; Manhiça, Mozambique; Mirzapur, Bangladesh; Kolkata, India; and Karachi, Pakistan. Data was collected for 8,592 case children aged <5 y old experiencing MSD and for 12,390 asymptomatic age, gender, and neighborhood-matched controls. An MSD case was defined as a child with a diarrheal illness <7 d duration comprising ≥3 loose stools in 24 h and ≥1 of the following: sunken eyes, skin tenting, dysentery, intravenous (IV) rehydration, or hospitalization. Site-specific conditional logistic regression models were used to explore the association between sanitation and hygiene exposures and MSD. Most households at six sites (>93%) had access to a sanitation facility, while 70% of households in rural Kenya had access to a facility. Practicing open defecation was a risk factor for MSD in children <5 y old in Kenya. Sharing sanitation facilities with 1–2 or ≥3 other households was a statistically significant risk factor for MSD in Kenya, Mali, Mozambique, and Pakistan. Among those with a designated handwashing area near the home, soap or ash were more frequently observed at control households and were significantly protective against MSD in Mozambique and India.

Conclusions - This study suggests that sharing a sanitation facility with just one to two other households can increase the risk of MSD in young children, compared to using a private facility. Interventions aimed at increasing access to private household sanitation facilities may reduce the burden of MSD in children. These findings support the current World Health Organization/ United Nations Children's Emergency Fund (UNICEF) system that categorizes shared sanitation as unimproved.

Interpreting the Global Enteric Multicenter Study (GEMS) Findings on Sanitation, Hygiene, and Diarrhea. PLoS Med, May 2016. Author: Jonny Crocker, Jamie Bartram
Full text: goo.gl/6SzZmr

The draft sanitation ladder for measuring SDG progress allows sharing of improved facilities by fewer than five households to count towards ending open defecation [19]. Higher rungs refer to private facilities and safe excreta management. The indicators also interpret access as including use, which was not included in GEMS. Future research should include indicators on use of facilities and excreta management.

Baker and colleagues provide valuable evidence that confirms that private sanitation often provides greater benefits than shared sanitation. Prior evidence suggests health benefits for use of any sanitation facility (including shared) when compared to open defecation [8–10]. This study will inform policy and programming, yet shared facilities may still have a role in addressing open defecation in challenging settings. For reasons beyond just health such as dignity and gender equity [20,21], we should advocate for private access whenever possible.

Baker and colleagues present the best dataset yet on diarrheal disease associated with sanitation and hygiene. They provide compelling evidence on sanitation and hygiene risk factors for MSD and variability in that risk. Importantly, they also demonstrate the feasibility and value of rigorous data collection on health outcomes, something that future studies should develop yet further.