Some of the 12,000 attendees who flew to Miami for the largest Bitcoin event in history last weekend have started testing positive for Covid.

Bitcoin 2021 attracted crypto enthusiasts from around the world to the Mana Wynwood Convention Center in the arts and entertainment district of Miami. For three days, conference attendees huddled in overcrowded lecture halls, happy and hugging. It was the first major conference since the pandemic began, and many attendees said they were relieved to be among colleagues sharing messages and updates.

There was no mask requirement and no proof of compulsory vaccination for participation. Covid was just a topic of conversation in connection with everyone’s excitement about being on the other side of the pandemic.

This is of course until some conference participants said on Twitter that they had tested positive for the corona virus.

For full disclosure, I attended the show after receiving two doses of the Moderna vaccine this spring. Vaccination isn’t a 100% guarantee of immunity, but at the moment I have no symptoms. A lot of my conversations with Uber and Lyft drivers started with a discussion about vaccination together.

It remains to be seen whether the conference will ultimately be billed as a super spreader event.

It is unclear how many people are affected and whether the city of Miami had a contingency plan for such an outcome. The mayor’s office and conference organizers did not immediately respond to CNBC’s request for comment.

On Tuesday, Florida said it would no longer report daily Covid cases and deaths as vaccinations increase and move into the “next phase” of the pandemic. Florida reported an average of eight new cases per 100,000 residents last week, well below its pandemic high of 84 per 100,000, according to Johns Hopkins University.