The three West African countries most affected by the Ebola epidemic aren’t likely to reach a Jan. 1 target to treat everyone with the virus in isolation and safely bury those who have died, a top official of the World Health Organization said Monday.

“We’re planning on a full-on six-month effort to really get this thing to zero,” said Bruce Aylward, assistant director-general, during a news conference in Geneva.

While citing significant progress against Ebola, he said some of the biggest challenges lie ahead. “To get to zero, we must find every single case,” he said. “You have to hunt the virus.”

Aylward was referring to contact tracing, a labor-intensive task in which teams track down every person who came into direct contact with a sick Ebola patient.

Forty-five counties, districts or prefectures are in Liberia, Guinea and Sierra Leone, and each jurisdiction has some capability to do contact tracing. But to be effective, the task requires about 20,000 tracers, and there are just 5,000 to 6,000, Aylward said.

The United Nations says the rate of transmission of Ebola fluctuates daily in Sierra Leone, but there are signs of progress in battling virus. (Reuters)

He said the effort would require additional international experts as well as large contingents of local workers.

“That needs to be scaled up with much greater rigor,” Aylward said, referring to the overall mobilization.

The latest WHO report shows 16,899 cases of Ebola in the three countries, including nearly 6,000 deaths. The heaviest toll has taken place in Liberia, which has 7,635 cases, including 3,145 deaths.

Two months ago, the United Nations set a target of having 70 percent of Ebola victims buried safely and 70 percent of Ebola patients treated in isolation beds within 60 days. All three countries have met the Dec. 1 target for safe burials, but only Liberia and Guinea have met that Dec. 1 target of having 70 percent of patients treated in isolation beds, Aylward said.

Sierra Leone does not have enough treatment beds to isolate Ebola patients in the western part of the country, he said. Once several treatment centers open in the next few weeks, the country will most likely meet the target then, Aylward said.

U.N. Ebola chief David Nabarro, speaking to reporters in Freetown, Sierra Leone, said, “the intensity of the Ebola transmission in some parts of Sierra Leone is very high, and the situation is getting serious each day and could worsen.”

Although Guinea has met both targets, Aylward said there is a “geographic mismatch” because treatment beds are highly concentrated in two areas, but Ebola cases have spread to 16 prefectures, nearly double from the end of September.

The international response of the past two months has shown that “you can close the yawning gap between the amount of disease and the response capacity,” he said. But no one can let down their guard.

“Just because you can catch up with Ebola doesn’t mean you will in all areas,” Aylward said.