The Ebola outbreak that has killed around 250 in central Africa is spreading faster than medical aid can be delivered – and experts fear it has reached Brazil.

A rare type of the fatal disease is ravaging the Democratic Republic of the Congo (DRC), with more than 1,000 cases reported so far.

The charity Doctors Without Borders warned: 'Never before has an Ebola outbreak recorded so many cases so soon after its declaration.'

Dr Alan Gonzalez, its deputy director of operations, said: 'Nobody knows the true scale and severity of this outbreak.' He added that his teams were 'witnessing a response that has not yet caught up to the rapid spread of the epidemic'.

Meanwhile, Brazilian health authorities are investigating two suspected cases of Ebola.

A 37-year-old man from the DRC has been isolated after showing 'symptoms meeting the definition of a suspected case' of Ebola, Sao Paulo state government said. Rio de Janeiro state health officials have introduced emergency measures after a man from Uganda exhibited 'viral symptoms'.

Ebola is caught from contact with the body fluids of an infected person or wild animal. Symptoms include nausea, rashes and bleeding from the ears, eyes, nose and mouth.

The current strain is known as Bundibugyo virus, for which there is no vaccine. Despite fears that it may spread to other nations, the World Health Organisation (WHO) has told countries not to close their borders, as this encourages travellers from disease hotspots to lie when crossing checkpoints.

However, America has banned entry to non-US citizens from DRC, Uganda and South Sudan, and Rwanda and Uganda have shut their borders. WHO Director-General Tedros Adhanom Ghebreyesus said such actions 'discourage the transparency that saves lives'.