The Bitcoin 2021 conference may have come and gone, but it’s having a lingering impact as attendees are beginning to test positive for COVID-19.

The Bitcoin convention was held last weekend in Miami, with some 12,000 attendees. As one of the first in-person events to happen since the pandemic’s outbreak, Bitcoin 2021 had no mask mandates or proof-of-vaccination requirements. People came from all over the world, mingling for three days.

In the aftermath of the event, people started testing positive, leading some to label the conference a “super spreader event.”

https://twitter.com/MiguelICarlos/status/1403079171505418240?s=20

Some Twitter users are already condemning those who attended without being vaccinated, saying it showed reckless disregard for the health of others.

I can’t believe people attended a massive in person conference without being vaccinated. It’s not just risky for themselves but it is reckless in regards to others

— CryptoRiot (@CryptoRiot1) June 10, 2021

While it’s not clear how many have been infected, some users indicated entire groups of people they were hanging out with have all tested positive.

Everyone who I hung out with in Miami got covid. Luckily for me I hung out about one feet above everyone

— Larry Cermak (@lawmaster) June 10, 2021

Bitcoin 2021 illustrates the challenges event holders will continue to face, despite rising vaccination numbers.