US: The Ebola epidemic in West Africa could be completely over by the end of the year if efforts to root out new cases are kept up, the WHO chief said Thursday.

World Health Organization director Margaret Chan cautioned there could be setbacks in the coming months but said Guinea, Liberia and Sierra Leone could begin 2016 completely Ebola-free.

“If the current intensity of case detection and contact tracing is sustained, the virus could be soundly defeated by the end of this year,” Chan told the United Nations Security Council.

“That means getting to zero and staying at zero,” she said during a special meeting on the disease.

Around 11,300 people have died from Ebola since late 2013 in the world’s worst outbreak of the often fatal illness that began in Guinea and spread to neighboring Sierra Leone and Liberia. 

Liberia, the hardest-hit country, was declared Ebola-free in May, but six new cases last month raised fears that the virus had not been completely beaten back.

Chan said that new cases in Liberia had again stopped and only three cases per week had been reported in Guinea and Sierra Leone over the past two weeks. 

This represents the lowest numbers seen in well over a year, she said.

Earlier this month, the medical aid group Doctors Without Borders (MSF), which has been on the frontlines of the Ebola battle, warned that the epidemic was by no means over.

“The Ebola epidemic in West Africa is far from under control,” according to Joanne Liu, who heads MSF.

Cases are still reported weekly, new communities are being infected and bodies are being buried in secret—a major problem for a disease transmitted though contact with body fluids, she wrote in the science journal Nature.

The WHO chief cautioned against “a false sense of security,” warning that a single undetected case can ignite a major flare-up.

Chan stressed that 13,000 survivors of the outbreak were struggling with long-term complications such as severe joint pains and visual impairments that can lead to blindness.