UNITED NATIONS - The United Nations on Wednesday called for more efforts in the last phases of the fight against Ebola to bring the number of cases down to zero.

The UN Special Envoy on Ebola David Nabarro told the General Assembly at a meeting that the final phase of "getting to zero" cases may well be the hardest, saying the hunt to track down the virus is "like looking for needles in haystacks."

"We are focusing on constant vigilance, we are focusing of proper surveillance and then we will get to zero cases," Nabarro told reports after his briefing.

Having strong surveillance capabilities on the ground to identify people with Ebola, to confirm diagnosis, to quickly arrangement arrange effective treatment, to identify people that are their contacts and to keep those people under review for 21 days is "a really difficult task," especially as these tasks must be coordinated through 63 different government structures in an area the size of France, he said.

Speaking to the General Assembly, UN Secretary-General Ban Ki- moon stressed we face "a critical turning point" as the pattern of the outbreak has changed, with a significant decline in the number of new cases in the three affected countries. However, he noted that incidence rates rose again in Guinea and Sierra Leone in recent weeks.

"More than half of those newly infected have not been in contact with people known to have had Ebola. This reminds us that setbacks can quickly follow apparent gains, and highlights the need for constant vigilance and active surveillance, even in unaffected areas," Ban said.

He appealed to the Assembly, "Let us provide the resources needed to get to zero" the number of Ebola cases in the current outbreak.

Urging efforts to ensure that reconstruction and recovery can occur without delay, the UN chief called on all responders to redouble their efforts, and on donors to "stay the course."

In his remarks, Assembly President Sam Kutesa said that while the international community should feel heartened by the progress that has been made against the virus in the most affected countries Guinea, Sierra Leone and Liberia "we cannot yet claim triumph over Ebola."

"The most-affected countries still face serious challenges, particularly with regard to their long-term social-economic recovery," he said. "The devastating impact of the Ebola outbreak could seriously compromise their sustainable development efforts."

To that end, Kutesa announced that a high-level international conference on Ebola on March 3 in Brussels, Belgium, is being organized to focus on the long-term needs of the region.

The latest statistics of the United Nations World Health Organization (WHO) show that nearly 23,000 people have been affected by Ebola with more than 9,200 deaths.

WHO also reported that despite improvements in case finding and management, burial practices, and community engagement, the decline in case incidence has stalled.