TORONTO (Reuters) - Early in the pandemic, a few cities and countries around the world began testing sewage for evidence of the coronavirus, hoping to detect rising infections early.Now some researchers are fine-tuning that strategy by moving upstream to test waste from single hospitals or other buildings, aiming to quickly pinpoint burgeoning COVID-19 outbreaks and stop them with testing and isolation. While the virus primarily spreads through droplets expelled from the mouth and nose, it can also be shed via human waste. Testing sewage is cheaper and less invasive than swabbing hundreds of people, and it could be done more frequently. With the virus again surging across much of the world, schools, hospitals and care homes badly need to catch new cases early. “What we’re trying to do is identify outbreaks before they happen,” said Francis Hassard, a lecturer at Cranfield University, part of a project that started collecting samples at 20 London secondary schools last month. Hassard’s UK government-funded team will expand sampling to at least 70 schools. The program is a research project, meant to test the approach, and is not yet a full-fledged surveillance system.