Health authorities are on high alert following a new Ebola outbreak in Africa that has already spread beyond the continent's borders.

Ebola, which triggers fever, vomiting and catastrophic bleeding, can prove fatal within just 24 hours of infection.

In an alarming update, the Democratic Republic of Congo's health ministry has confirmed that more than 130 people are believed to have died, with over 500 suspected cases recorded in the eastern region of the country.

An American citizen has also tested positive for the virus after being exposed while working in the DR Congo. The individual has since been flown to Germany for treatment, according to the Centres for Disease Control and Prevention (CDC), and is currently being treated in a specialist isolation ward at Berlin's Charité hospital.

Six further individuals have been identified as high-risk contacts and are expected to be transferred to Europe to undergo strict quarantine measures.

As the world grapples with yet another major health crisis, an American doctor who contracted Ebola while treating patients during the 2014 outbreak has spoken out with a stark warning.

Dr Craig Spencer told American outlet ABC News that he is "certain" the current outbreak is "much bigger" than the official figures suggest.

"My biggest concern about this outbreak is that we learned way too much way too quickly for this to be anything but really bad," Dr Spencer said. Dr Spencer tested positive for the deadly virus after treating patients in Guinea in 2014 while working for Médecins Sans Frontières, also known as Doctors Without Borders. Upon returning to the United States, he spent 19 days receiving treatment at Bellevue Hospital in Manhattan, New York.

"I was lucky enough to survive. And then a few months later, I went back to Guinea. As an epidemiologist helping run the national response for Doctors Without Borders in early 2015," Dr Spencer said.

When asked whether he would consider volunteering his expertise to assist with the current Ebola outbreak, he said: "I've already put my family through quite a bit. We'll see what comes out of this, but I'm happy to help."

Dr Spencer told ABC News that the American doctor who has recently contracted the disease weighs heavily on his mind.

"I unfortunately know exactly what it feels like to be in that situation, to be incredibly fearful, to have a disease that maybe you've seen the impact of and know that there's not a treatment for," Dr Spencer said, adding: "I'm thinking of him and his family."

Dr Spencer continues to practise emergency medicine at A&E, and also serves as a professor of public health at Brown University. He further noted that US President Donald Trump's decision to withdraw America from the World Health Organisation (WHO) has left the country ill-equipped to respond to the latest Ebola outbreak — one of Trump's first actions upon resuming office last year.

Dr Spencer's remarks follow US Secretary of State Marco Rubio's criticism of the WHO on Tuesday (May 19), when he told reporters the international health body was "a little late" in detecting the devastating Ebola outbreak in Africa.

"The lead is obviously going to be CDC and the World Health Organisation, which was a little late to identify this thing unfortunately," he said, via the Guardian.

Rubio revealed that the United States - which pledged approximately £9.7 million (USD$13 million) in aid despite extensive funding cuts last year - was aiming to establish around 50 treatment centres for Ebola in the DR Congo.

America's exit from the WHO also resulted in the international health body losing nearly a quarter of its workforce – roughly 2,000 positions – from a total staff of approximately 9,400.

Trump's decision to pull the US out of the WHO has been characterised by experts - particularly Georgetown University professor of global health Lawrence Gostin - as "sowing the seeds of the next pandemic".