Frustrated residents of Monrovia, who have been seeking treatment at an Ebola health center on Thursday, complained about delays they were facing, as Liberia, the country hardest-hit by the disease, cordoned off areas of its capital at one point to slow transmission.

The Ebola outbreak’s unprecedented scale has overwhelmed already weak health systems: A shortage of ambulances has stranded many of the sick at home, others have been turned away from teeming treatment centers and bodies have sometimes not been buried for days.

The World Health Organization warned on Thursday that Liberia needs 1,500 more beds than are currently being set up.

The lack of capacity at labs that perform the tests for Ebola is also hindering experts’ ability to track the outbreak.

The Ebola outbreak is believed to have sickened more than 6,200 people in West Africa and killed nearly 3,000.