Mali is rushing to impose tougher measures to contain the spread of Ebola after recording a new case of the disease in the West African nation's capital, health officials said on Thursday.

The world's worst epidemic of the hemorrhagic fever on record has killed at least 5,160 people since it erupted in March in West Africa, a region dogged by poverty and poor healthcare. It has ravaged Liberia, Sierra Leone and Guinea and spurred a global watch for its spread.

Liberia, the country hardest hit by the outbreak, announced it would not renew a state of emergency, highlighting at least some recent progress in neutralizing the virus there.

In Mali, which shares an 800-km (500-mile) border with Guinea, a 25-year-old health worker became the country's second confirmed case of Ebola on Tuesday, although four deaths in Mail have been attributed to the disease.

The nurse died after treating a Muslim Imam from Guinea, who suffered from Ebola-like symptoms that were not recognized.

On Thursday a doctor at the same clinic was also revealed to be infected. A woman who was being treated at Bamako's Gabriel Toure Hospital - the city's second largest - tested positive as well.

"We tested two cases today. One was negative but the other preliminary test was positive. We're waiting for the definitive results," health ministry spokesman Daou Markatié said. "She had participated in the washing of the imam's body."

More than 90 people were quarantined in the capital Bamako after the nurse's death, and health workers are now seeking to trace an unknown number of contact cases.

"The president of the republic has asked the prime minister to look urgently at the entire system put in place to fight Ebola and to strengthen health controls at the different frontier posts," a government statement said.

But officials said there were no plans to close the border, even though the nurse had been infected by a man who arrived from Guinea.

President Ibrahim Boubacar Keïta urged the World Health Organization (WHO) and health services in Mali and neighboring states to set up a permanent information exchange to improve awareness about public health and hygiene.

Fueling hope of progress in containing the disease, Liberian President Ellen Johnson Sirleaf said she would not seek to extend a state of emergency imposed in August.

On Wednesday, the WHO said the Ebola death toll in Guinea, Liberia and Sierra Leone had reached 5,147 out of 14,068 cases as of Nov. 9, with 13 more deaths and 30 cases recorded in Nigeria, Senegal, Mali, Spain and the United States. It said there was some evidence that case incidence was no longer increasing nationally in Guinea and Liberia, but steep increases persist in Sierra Leone.

Some 421 new infections were reported in Sierra Leone in the week to Nov. 9, especially in the west and north, and the virus is still spreading intensely in Freetown, the capital, as well as in Guinea's southwest near the Liberian border, the WHO said.

The Liberian emergency, which allowed authorities to curb movement in the areas worst affected, officially expired earlier this month. Sirleaf said a night curfew would remain in effect.

CLINIC IN LOCKDOWN

The death of the nurse in Mali forced a lockdown in the clinic where she had worked.

The Pasteur Clinic, one of Bamako's leading medical facilities and the default health center for expatriates, was being guarded by U.N. peacekeepers with armored personnel carriers and by Malian security forces, witnesses said.

Mali's first case of Ebola was a 2-year-old girl who had been infected in Guinea and died last month.

Just as the people who had been in contact with her finished their 21 days of quarantine, Mali must now trace those who had contact with the nurse and those infected with her.

Last September, the International Monetary Fund provided $130 million to Guinea, Liberia and Sierra Leone in September to help them cope with the economic impact of Ebola. On Thursday, it said it would discuss debt relief for the three countries with Group of 20 leaders meeting in Australia this week.

In Washington, the Obama administration tried to assure a skeptical Senate that its efforts to combat Ebola were bearing fruit and urged lawmakers to approve $6.2 billion in new emergency funds for that purpose.

Tens of thousands of nurses across the United States staged protest rallies and strikes on Wednesday over what they say is insufficient protection for health workers dealing with patients possibly stricken with Ebola.

The global medical charity Medecins sans Frontieres said on Thursday that clinical trials of three potential Ebola treatments would begin in December at MSF medical centers in Guinea and Liberia.