LONDON (AP) — Britain’s main nurses’ union has warned that exhaustion and surging coronavirus cases among medical staff are pushing them to the breaking point. That is adding to pressure on the government for new restrictions to curb record numbers of infections driven by the omicron variant. The warning Monday throws into stark relief the unpalatable choice Prime Minister Boris Johnson faces: wreck holiday plans for millions for a second year running, or face a potential tidal wave of cases and disruption. Many governments in Europe and the U.S. are confronting similar dilemmas over how hard to come down on omicron.