Some of the 12,000 attendees who flew into Miami last weekend for the biggest bitcoin event in history have started testing positive for Covid.

Bitcoin 2021 drew crypto enthusiasts from around the world to the Mana Wynwood convention center in Miami’s arts and entertainment district. For three days, conference goers packed into crowded auditoriums, glad-handed and hugged. It was the first major conference since the pandemic started, and many attendees said they were relieved to be out among colleagues trading news and updates.

There was no mask mandate and no proof-of-vaccination requirement to attend. Covid was only a talking point in the context of how thrilled everyone was to have arrived at the other side of the pandemic.

That is, of course, until some conference participants took to Twitter to say they had tested positive for the coronavirus.

In the spirit of full disclosure, I attended the show after receiving two doses of the Moderna vaccine this spring. A vaccination isn’t a 100% guarantee of immunity, but at the moment, I’m not presenting any symptoms. Many of my conversations with Uber and Lyft drivers started with a mutual discussion of having been vaccinated.

Whether the conference is ultimately billed as a super spreader event remains to be seen.

It is unclear how many people have been affected and whether the city of Miami had a contingency plan in place for this kind of outcome. The mayor’s office did not immediately respond to CNBC’s request for comment.

Conference organizers told CNBC that all attendees were provided with “the current recommendations of the CDC and State of Florida,” and they had expressed to the audience that “those who were high risk or hadn’t been vaccinated should consider waiting until next year.”

On Tuesday, Florida said it will no longer report daily Covid cases and fatalities as vaccinations rise and it begins shifting to the “next phase” of the pandemic. Florida reported an average of eight new cases per 100,000 residents over the past week, according to data compiled by Johns Hopkins University, far below its pandemic high of 84 per 100,000.