ANASTASIA MOLONEY FROM Bogota to Athens, the coronavirus pandemic has revealed pockets of once invisible urban poverty, prompting some mayors to target the cities' poorest for new health and welfare measures, a top health official said on Thursday. About half of the world's population live in urban areas and city mayors are on the frontline of the COVID-19 response, often deciding when to introduce and lift lockdowns and taking responsibility for the running of hospitals. Some mayors have become "urban health champions" introducing measures to help the poorest, World Health Organization Director-General Tedros Adhanom Ghebreyesus told a webinar. "Nowhere has…