Over a thousand festival-goers caught coronavirus after attending a 20,000-person event in Utrecht, leading the city's mayor to apologise, saying it was ‘an error of judgment’. Health authorities say the disease spread over both days of the outdoor music festival, leading to the highest count of infections that could be traced back to a single event. It was a ‘test-for-entry event’, meaning visitors were allowed if they presented a vaccination card, held a negative coronavirus test, or had had Covid-19 recently. Authorities now believe that the time frame (40 hours) for negative tests was too long. Dutch caretaker prime minister Mark Rutte apologised for his government's quick relaxation of safeguards, admitting what they thought was possible was wrong after all. Cases jumped fivefold in one week.