When polio vaccinators fanned out across the Democratic Republic of the Congo last year to stop an outbreak, they carried a powerful new tool: cellphones that tracked their progress as they went from door to door. Equipped with an app, the phones send data back to a command center where staff can see missed homes on a digital map and redirect teams on the ground. The country is helping pioneer geospatial tracking to stop polio outbreaks. Vaccinators, trained by the World Health Organization, hit the streets in June 2023, armed with hundreds of phones, after an outbreak of vaccine-derived poliovirus type 1. Read more about using phones to combat polio.