Organizers of the Boston Marathon, the planet’s most celebrated footrace, are postponing the event until Sept. 14 because of concerns over the coronavirus pandemic, Boston Mayor Marty Walsh announced Friday.

The Boston Athletic Association, which oversees the marathon, had held off deciding the fate of the April 20 race even as other high-profile sporting events were canceled or postponed around the globe.

But pressure had mounted in recent weeks from officials in Boston and the seven cities and towns along the 26.2-mile (42.2-kilometer) course. Some had expressed worries not only for the health of the 31,000 registered runners but also the estimated 1 million spectators who traditionally line the route, giving athletes hand slaps, high fives and even kisses as they pass.

“We want to make sure that we keep people safe,” the mayor said at a news conference. He stressed that people shouldn’t attempt to run the race course in April when the marathon would have taken place, as some in the running community have suggested.

President Donald Trump’s order restricting most Europeans’ travel to the United States over the coronavirus complicated efforts to salvage the race. Thousands of runners come from Europe to compete at Boston.

For most people, the new coronavirus causes only mild or moderate symptoms, such as fever and cough. For some, especially older adults and people with existing health problems, it can cause more severe illness, including pneumonia, and death.

The vast majority of people recover from the new virus. According to the World Health Organization, people with mild illness recover in about two weeks, while those with more severe illness may take three to six weeks to recover.

The Boston Marathon has never been canceled outright since its first running in 1897, though there was a de facto cancellation in 1918, when the end of World War I and a global influenza pandemic prompted organizers to switch to a relay race format.

Until Friday, not even the Great Depression or ferocious storms had interrupted the 124-year-old race, a bucket list quest for runners worldwide. About a third of this year’s field were from outside the U.S.

Officials acknowledged postponing the race is a big undertaking but that canceling it outright would have been even more harmful.

Walsh had said the marathon pumps $211 million a year into the city’s economy — not counting the millions more that runners raise for charities.

“It won’t look right on the calendar,” said Gov. Charlie Baker. “But it’s the right thing to do.”

Baker has already declared a state of emergency, and race organizers had said they were in close contact with the federal Centers for Disease Control and Prevention and the World Health Organization.

In recent days, the Rome Marathon was canceled, the Paris Marathon was postponed from April 5 to Oct. 18 and the Barcelona Marathon was postponed from March 15 to Oct. 25, all over concerns around COVID-19.

“It’s been in Ohio as early as the mid-1850s at least, brought in as an ornamental plant because of its unique foliage and white flowers,” Gardner said. “It was actually planted in people’s landscaping, and it has been spreading.”

This month’s Tokyo Marathon was expected to have 38,000 participants but was limited to elite runners due to concerns over the outbreak of the virus in Japan. And spectators at the Los Angeles Marathon, held earlier this month, were advised to practice social distancing.

Walsh said there was never a consideration to run the race with a limited field of elite runners.

“That’s not the Boston Marathon. We’re an inclusive marathon,” he said. “The Boston Marathon is for everyone..”