Global coronavirus cases top 20 million after doubling in 45 days

The number of confirmed coronavirus cases worldwide topped 20 million on Tuesday, more than half of them from the U.S., India and Brazil.

Health officials believe the actual number is much higher than that tally kept by Johns Hopkins University, given testing limitations and the fact that as many as 40% of those who are infected have no symptoms.

It took six months or so to get to 10 million cases after the virus first appeared in central China late last year. It took just over six weeks for that...