South Korea has reported more than 500 new coronavirus cases for the third straight day, the speed of viral spread unseen since the worst wave of the outbreak in spring.

According to AP, the 504 cases reported by the Korea Disease Control and Prevention brought the national caseload to 33,375, including 522 deaths.

Around 330 of the new cases came from the densely populated Seoul metropolitan area, home to about half of the country’s 51 million population, where health workers are struggling to stem transmissions linked to hospitals, schools, saunas, gyms and army units.

Officials reimposed some of the restrictions this week and could be forced to clamp down on economic activities further if transmissions don’t slow.