A daycare has repeated outbreaks of fecal-oral illness among toddlers. Which single intervention is likely to have the greatest immediate impact on reducing transmission and why?

Universal masking of toddlers at all times during the day, because respiratory masks are the primary control for fecal-oral pathogens found in daycare centers.

Implementing strict handwashing protocols for staff and children after toilet use and before food handling, because hand hygiene removes fecal microbes before they contaminate food or shared items and interrupts the fecal-oral route.

Ceasing diaper changes and relying on toddlers to change themselves to reduce adult contact, because less adult contact eliminates adult-mediated transmission chains.

Replacing all toys with wooden toys only, because plastic toys inherently support fecal-oral transmission while wooden toys eliminate microbial survival completely.