The COVID-19 death toll in the United States has soared to more than 170,000, just 18 days after the nation marked 150,000 lives lost.As cases have increased in the U.S., the lull between grim milestones has grown shorter. It took 54 days for the number of people killed by the virus to go from one to 50,000, and then 34 days to cross 100,000 mark