Number of confirmed coronavirus cases reaches 1 million worldwide; Over 51,000 have died

The number of confirmed COVID-19 cases reached the 1 million mark on Thursday, just one day after topping 900,000 and two days after hitting 800,000, according to figures compiled by Johns Hopkins University. The global death toll is now over 51,000.

World Health Organization Director-General Dr. Tedros Adhanom Ghebreyesus said Wednesday he's "deeply concerned about the rapid escalation and global spread of infection."

"Over the past five weeks, we have witnessed a near exponential growth in the number of new COVID-19 cases, reaching almost every country, territory and area," he said.

The real figures, however, are believed to be much higher because of testing shortages, differences in counting the dead and large numbers of mild cases that have gone unreported.

The United States is the country with the most confirmed cases, at more than 225,000, followed by Italy and Spain. President Donald Trump's administration is projecting that 100,000 to 240,000 will likely die, even if the government's social distancing measures are maintained until their April 30 deadline. The U.S. has recorded more than 5,000 deaths.

New York City accounting for about 1 out of 4 dead, and New York Governor Andrew Cuomo said projections suggest the crisis in New York will peak at the end of April, with a high death rate continuing through July.

"Let's cooperate to address that in New York because it's going to be in your town tomorrow," he warned. "If we learn how to do it right here - or learn how to do it the best we can, because there is no right, it's only the best we can - then we can work cooperatively all across this country."

ABC News and The Associated Press contributed to this report.