The number of K-12 students in the United States whose schools have closed or are scheduled to shutter because of the spread of the novel coronavirus has surpassed 3.5 million — and more are expected.

Around the world, the number of students whose education has been interrupted by the virus has soared to 391.5 million students, according to UNESCO.

The World Health Organization says that the number of confirmed cases of covid-19, the disease caused by the coronavirus, has surpassed 126,000, and that more than 4,600 people have died. The death toll in the United States had reached 38 by early Thursday, with more than 1,300 cases diagnosed. Experts warned they expect the crisis to worsen in the next few weeks.

As of late Thursday, UNESCO reported, 29 countries had shuttered schools and universities nationwide. That was several million more students than earlier Thursday, showing the continuing and swift impact from the spread of the coronavirus.

An additional 20 countries have had localized school closures to prevent or contain the virus, UNESCO said.

The United States has seen a rapid rise in the number of students affected by school closures, according to a tally being kept by Education Week.

On Wednesday, the number of K-12 students affected by closings or planned closings was slightly more than 1 million. By Thursday morning, it had risen to 1.3 million students. By late Thursday, Maryland announced it was closing all schools from March 16 through 27, affecting more than 889,000 students, and so did Ohio, affecting some 1.7 million students.

Schools have closed for a host of reasons, including someone being diagnosed or exposed with the virus. In other cases, they close for cleaning or so teachers can be trained in online education.

That total does not include the hundreds of thousands of university students whose schools are closing. They are being sent home, with plans for them to take courses online, and many are being told not to return for the rest of the school year.

More than 100 colleges and universities have closed, according to this list being kept by Bryan Alexander, a scholar at Georgetown University.

States with partial K-12 closures, according to Education Week, include California, Colorado, Florida, Georgia, Idaho, Illinois, Indiana, Kentucky, Massachusetts, Missouri, Nebraska, New Hampshire, New York, New Jersey, Pennsylvania, Rhode Island, South Carolina, Tennessee, Virginia, Vermont and Washington. The District planned to close schools March 16 for a day of teacher training related to the virus.

You can see data on U.S. closings here on EdWeek’s page, and the information on UNESCO’s page here.