Urgent action is desperately needed to prevent the ebola outbreak from becoming as deadly and prolific as the AIDS virus, a leading health expert has warned.

Tom Frieden, from the Centers for Disease Control and Prevention (CDC), said "it's going to be a long fight" to stop the disease, which has killed 3,900 people, from spreading.

"We have to work now so that it is not the world's next Aids," he told the heads of the United Nations, World Bank and International Monetary Fund in Washington.

"I would say that in the 30 years I've been working in public health, the only thing like this has been Aids."

Mr Frieden's comments were echoed by UN Secretary-General Ban Ki-moon, who insisted that the world needs to put 20 times more effort into quashing the ebola virus once and for all.

Their warnings came as Thomas Eric Duncan, the first person to be diagnosed with ebola in the United States, died from the disease at a hospital in Texas.

Meanwhile, a Spanish nurse remains at "serious risk" after she became the first-known patient to contract ebola outside Africa.

Teresa Romero is "very ill and her life is at serious risk as a consequence of the virus", according to the Spanish government.

According to the CDC, the number of ebola cases worldwide could exceed 1.4 million by January if the world's response continues to be slower than the spread of the virus.