Daily coronavirus case numbers in the US are at levels not seen since the summer, and more than a dozen states set record highs for Covid-19 hospitalizations in the past week -- yet more evidence, experts say, of a difficult fall and winter ahead. The country's seven-day average of new daily cases was above 58,300 as of Monday -- a level not seen since the first week of August, and climbing closer to the summer's peak of 67,200 on July 22. Average daily new cases have soared 70% since September 12, when the country was at a two-month low of about 34,300.