The United States reported a 25% drop in new cases of COVID-19 to about 825,000 last week, the biggest fall since the pandemic started, although health officials said they were worried new variants of the virus could slow or reverse this progress. New cases of the virus have now fallen for four weeks in a row to the lowest level since early November, according to a Reuters analysis of state and county reports. The steepest drop was in California, where cases in the week ended Feb. 7 fell 48%. Only Oregon, Puerto Rico, Arkansas and Vermont saw cases rise. (Open in an external browser to see a state-by-state graphic.) At least three new variants of […]