As the deadline approached Wednesday for would-be Bloomies to sign up for a virtual race, organizers started to see a feverish demand that didn’t slow.

“We moved quickly from 18,000 to 19,000 and into the 20,000s, in a matter of days leading up to the 26th,” said Jon Neill, Bloomsday race director. “It was extraordinary to see.”

It was also difficult for those putting on the three-day virtual event next month to stop.

So organizers have kept online registration open for Bloomsday, as the number of entrants creeps closer to the size of the traditional May road race, which last year totaled 35,244 finishers.

Neill said his team was emboldened to extend online registration after it began mailing some 16,000 racing bibs out to early registrants last week. Those bibs began arriving in runners’ mailboxes on schedule on Tuesday, Wednesday and Thursday, meaning there was still some buffer room before the Sept. 18-20 virtual race dates to get runners their competition materials.

“We’ve never done a mailing like this,” Neill said. “We had the advantage of a trade shot, with runner check-in at the convention center.”

Bloomsday made the decision to go virtual at the end of July, canceling an in-person event in September that was intended to replace the traditional May run that has taken place every year since 1977.

Registered runners will receive a bib, and must run a course the same 12-kilometer (7.46-mile) distance as the Bloomsday course over the three-day period in September. After uploading their time to the race’s website, virtual Bloomies will receive finisher T-shirts, also through the mail.

Neill said the streaks of 82 “Perennials,” finishers of all 43 Bloomsday races to date, will remain alive this year. They’ve all signed up for the virtual run.

The race director, who took over for race founder Don Kardong last summer, said he was also heartened by the decision of many runners to observe Bloomsday in early May. Several hundred runners completed the traditional course, some even starting at the usual time early Sunday morning.

“There were so many great things that emerged from that day,” Neill said. “People just taking the time, at 9 a.m., and the traditional gun start, to go do a run, go do a walk in the park, or some other city. That was really fun to see.”

Neill also applauded the work of race organizers in Coeur d’Alene, who staged a successful marathon with a staggered start this past weekend. With tens of thousands of participants and a road course, such an option wouldn’t work for Bloomsday without severely limiting participation, Neill said, something Bloomsday organizers didn’t want.

“We wanted to make sure that we had the widest participation possible,” he said. “For us to abbreviate the course, abbreviate the participation, that wasn’t something that we were willing to do.”

For now, those interested in the virtual race can continue to sign up at bloomsdayrun.org. The fee is a little less than $25, and includes a bib and a finisher T-shirt for runners who post their time by Sept. 20.