New York State’s long-feared surge of coronavirus cases has begun, thrusting the medical system toward a crisis point. In a startlingly quick ascent, officials reported on Friday that the state was closing in on 8,000 positive tests, about half the cases in the country. The number was 10 times higher than what was reported earlier in the week. In the Bronx, doctors at Lincoln Medical and Mental Health Center say they have only a few remaining ventilators for patients who need them to breathe. In Brooklyn, doctors at Kings County Hospital Center say they are so low on supplies that...