The decision to hold the festival five weeks ago came at a different point in the crisis, before a single person had tested positive in Miami-Dade County, said Rea Carey, executive director of the National L.G.B.T.Q. Task Force. The event ended the day before the World Health Organization declared the virus a pandemic.

“It points to what we didn’t know at the time,” she said. “If we had had the information that is available now, the information that has become available after Winter Party as this pandemic has played out, we would have made a different decision.”

Photos of the festival show hundreds of people crammed in front of a stage under neon lights, dancing, hugging and practicing little social distancing.

Ms. Diaz, 42, got a fever on March 15. The next day her girlfriend was also sick. By the time Ms. Diaz was confirmed positive for Covid-19, she had been grocery shopping, gone to the pharmacy and spent time with her employer’s 80-year-old father and 14-year-old daughter.