Hospital capacity is being tested in the nation’s hardest-hit areas by a third wave of COVID-19 as a growing number of severely ill patients occupy a dwindling number of available beds.

The number of patients severely ill with the disease in Japan reached 280 on Thursday — the highest since August — in a concerning trend that could overwhelm hospitals, health care facilities and intensive care units, delaying treatment for patients in critical condition.

More than 50% of hospital beds for COVID-19 patients are occupied in Tokyo, Kanagawa, Osaka and Hokkaido prefectures following an abrupt surge in new cases that began last week. Experts are concerned about the prolonged pressure this will put on front-line workers.