Another day, another mind-boggling milestone: 4 million people in the U.S. have tested positive for the coronavirus. The U.S. hit the 3 million mark just 15 days ago. That's according to a tracker from Johns Hopkins University. More than 143,700 people have died from the virus in the U.S. — nearly twice as many as Brazil, the country with the second-highest number of fatalities. Case numbers continue to rise in most U.S. states and territories. While confirmed cases have surpassed 4 million, federal health officials have said the actual number is likely many times higher. "Our best estimate right now is that for every case that was reported, there actually were 10 other infections," Dr. Robert Redfield, director of the CDC, said last month.