Authorities are having trouble figuring out how many more people are getting Ebola in Liberia and Sierra Leone and where the hotspots are in those countries, according to the UN's top Ebola official in West Africa.

This is harming efforts to get control of the outbreak, Anthony Banbury said on Tuesday.

Over the past week, the US said, Banbury met the presidents of Guinea, Sierra Leone and Liberia, where Ebola has infected at least 10,000 people and killed roughly half of them, as he focuses on adapting an operational framework for international anti-Ebola efforts.

"The challenge is good information, because information helps tell us where the disease is, how it's spreading and where we need to target our resources," Banbury told the Associated Press by phone from the Ghanaian capital of Accra, where the UN Mission for Ebola Emergency Response, or UNMEER, is based.

Health experts say the key to stopping Ebola is breaking the chain of transmission by tracing and isolating those who have had contact with Ebola patients or victims. Health-care workers cannot do that if they do not know where new cases are emerging.

"And unfortunately, we don't have good data from a lot of areas. We don't know exactly what is happening," Banbury, the UNMEER chief, said.

He said he is hoping for a new approach in Liberia as the UN and its partners work to improve the capacity of communities to safely bury victims.

Widespread Ebola fear

Separately, the president of the World Bank said Guinea, Sierra Leone and Liberia need at least 5,000 more health workers to effectively fight the epidemic.

Jim Yong Kim said on Tuesday that he is worried about where those health workers can be found given the widespread fear of Ebola.

Quarantining health workers returning to their home countries could also hurt recruitment efforts.

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Jim spoke alongside Ban Ki-moon, UN secretary-general, and Nkosazana Dlamini-Zuma, African Union (AU) chairperson, in Addis Ababa, Ethiopia, where the AU is headquartered.

Although Western governments and aid groups have stepped up Ebola aid in recent months, the UN says more support is needed.

The UN's target is to have 70 percent of Ebola cases getting access to a treatment centre and to achieve a similar percentage for safe Ebola burials.

Ban said the transmission of the virus continues to outpace the international community's response.

He appealed to the AU's 54 member states not to impose Ebola-related travel restrictions or close their borders. Some already have.

Dlamini-Zuma said AU states had pledged to send more than 2,000 health workers to West Africa.

Cases in the US

In the US, a nurse who fuelled Ebola fears by flying to Cleveland after being infected by her dying patient in Dallas was released on Tuesday from a hospital isolation unit, where doctors defended her as a courageous and passionate front-line caregiver.

Another nurse, held for days against her will in a medical tent in New Jersey after volunteering in West Africa, was in an undisclosed location in Maine, objecting to quarantine rules as overly restrictive.

Lawyers now represent both Amber Vinson, who contracted the virus while caring for a Liberian visitor to Texas, and Kaci Hickox, who is challenging the mandatory quarantines that some states have imposed on anyone who came into contact with Ebola victims.

In another Ebola-related development, in Geneva, the Swiss agency that regulates new drugs said on Tuesday it has approved an application for a clinical trial with an experimental Ebola vaccine at the Lausanne University Hospital.

Swissmedic said the trial will be conducted among 120 volunteer participants with support from the UN World Health Organisation.

The experimental vaccine is to be initially administered on healthy volunteers who will be sent as medical staff to fight the Ebola epidemic in West Africa.

In a statement, the Bern-based Swiss government agency said the trial continues a series that began in the US, Britain and Mali, using a vaccine based on a genetically modified chimpanzee adenovirus.

Source: Agencies