While deaths from the coronavirus in the U.S. are mounting rapidly, public health experts are seeing a flicker of good news: The second surge of confirmed cases appears to be leveling off. Scientists aren’t celebrating by any means, warning that the trend is driven by four big, hard-hit places — Arizona, California, Florida and Texas — and that cases are rising in close to 30 states in all, with the outbreak’s center of gravity seemingly shifting from the Sun Belt toward the Midwest. Some experts wonder whether the apparent caseload improvements will endure. It’s also not clear when deaths will start coming down. COVID-19 deaths do not move in perfect lockstep with the infection curve, for the simple reason that it can take weeks to get sick and die from the virus. The future? “I think it’s very difficult to predict,” said Dr. Anthony Fauci, the government’s foremost infectious-disease expert.