FREETOWN, Sierra Leone — Acknowledging that the Ebola epidemic sweeping Sierra Leone was worsening, officials here put hundreds of thousands more citizens under quarantine on Thursday, sealing off more than a quarter of the country and warning travelers not to get out of their vehicles in the districts under isolation.

Nearly all of the country’s 14 districts are now under either total or partial quarantine, with over one million people affected, as the disease advances into new areas. Infection rates have been rising in the capital, Freetown, a dangerous development because of the city’s density.

In an address to citizens late Wednesday night, President Ernest Bai Koroma acknowledged that the new quarantine orders would “definitely pose great difficulties for our people,” but he suggested that officials had little choice. Makeni, the largest city in the country’s Northern Province, is in one of the newly quarantined districts, and foreign health care workers are particularly worried about a surge in infections there.

In what appeared to be an acknowledgment that official statistics had so far been misleading, the government said the country’s plight was “worse than what was being reflected in reports,” adding that there was a “desperate need to step up our response.”