More than 1,900 people have died in the Ebola epidemic sweeping through West Africa, the head of the World Health Organization said Wednesday.

“As of this week, we are reporting 3,500 cases confirmed in Guinea, Sierra Leone and Liberia and more than 1,900 deaths — and the outbreak is rising,” Margaret Chan told reporters in Washington.

The latest toll represents a significant increase from the 1,552 deaths and 3,069 cases reported by the Geneva-based organization just days ago.

Speaking at a news conference, Chan said she hoped that, thanks to the global response to the crisis, transmission of the often fatal virus could be stopped in six to nine months.

“With this international response, coordinated response, the money is coming, the technical experts are coming, so we hope to stop the transmission in six to nine months,” Chan said.

Citing the WHO’s roadmap to fight the worst Ebola outbreak in history, she said that in countries with “very intense transmission” — Guinea, Sierra Leone and Liberia — “we would like to reverse the trend in three months.”

She said for countries with “localized transmission” such as the Democratic Republic of Congo and Senegal, the WHO “would like to stop all transmission within eight weeks.”