A university student infected with Ebola evaded health surveillance for weeks as he slipped into Senegal, carrying the deadly virus to a fifth West African nation showing how quarantines, border closures and flight bans have failed to contain the outbreak.

Now health officials must try to identify and monitor all of his contacts in Senegal's capital of Dakar — no small feat in a metropolitan area with more than 2 million people that serves as a major transportation hub and popular destination for European tourists.

The student from Guinea finally showed up at a hospital in Dakar on Tuesday, seeking treatment but concealing that he had been in contact with other Ebola victims, Health Minister Awa Marie Coll Seck said.

The next day, an epidemiological surveillance team in Guinea alerted Senegalese authorities that they had lost track of a person who had had contact with sick people. The team said that the person disappeared three weeks ago and may have come to Senegal.

'I don't see how, with the current measures, we're going to control the outbreak.'- Mego Terzian

The student, who is in satisfactory condition, was tracked down in the Dakar hospital the next day and immediately quarantined, Seck said. Authorities also sent out a team to disinfect the home where he was staying.

Senegal is among the African nations banning flights from Guinea, Sierra Leone, Liberia and Nigeria, where the accelerating outbreak has killed more than 1,500 people. Senegal also has closed major border crossings, but West Africa's frontiers are so porous that it would be impossible to seal borders altogether.

As part of the ongoing international response, the United Nations will use Ghana as a base for supplies bound for countries affected by the outbreak. 

UN chief Ban Ki-moon had a telephone conversation on Friday evening with Ghana's President John Dramani Mahama, who agreed to let international agencies use Ghana's capital Accra as a base for air lifting supplies and personnel to affected countries, the Ghanaian presidency said in a statement on Friday.

"Using Accra as the logistics and coordination centre would therefore open a vital corridor to get urgently needed supplies and health personnel into the affected countries and areas," the statement said.

Regular international commercial flights to the affected countries have been suspended, making it difficult for supplies to reach them.

Senegal Ebola

A woman walks past the entrance to the University Hospital Fann, where a man is being treated for symptoms of the Ebola virus in Dakar, Senegal on Friday. (Jane Hahn/Associated Press)

​ Doctors Without Borders and other public health organizations say such measures hamper relief efforts and further stigmatize people from infected countries.

"The Senegal case is not unexpected. All countries in the region should be getting ready for a possible case of Ebola," said Peter Piot, a co-discoverer of Ebola who directs the London School of Hygiene and Tropical Medicine.

"I think it illustrates the ineffectiveness of closing borders and cancelling flights. People will still find a way to get around," Piot said.

Health officials instead call for checking travellers' symptoms at airports and land crossings.

More the 500 new cases were recorded this week, far outpacing the 400 cases from the week before, WHO announced Friday.

"Emergency action needs to be taken to reverse the situation to avoid a catastrophe," U.S. Centers for Disease Control and Prevention director Tom Frieden warned while visiting Sierra Leone on Friday.

Struggle to control outbreak

But a top official from Doctors Without Borders said "the World Health Organization can't handle" this crisis. Mego Terzian, the group's president for France, told France Inter radio that the U.N. Security Council should intervene and that countries with military medical units should get involved.

"We can't create a prison in the region and watch the Africans die," Terzian said.

Because there is no known cure for Ebola, doctors can only isolate the sick and try to help their immune systems fight off the disease. But one previously untested drug has been tried in this outbreak. It's still unclear whether it's effective. On Friday, a Liberian physician's assistant and a Congolese doctor who received the ZMapp drug in Liberia were expected to be released from the hospital.

The California-based company that makes ZMapp has said its supplies are exhausted, and it will take months to make more.Severe measures such as cordoning off entire neighbourhoods can backfire by provoking unrest and instability that makes controlling the disease even more difficult, he warned.

On Thursday, townspeople in Guinea, confused about efforts to disinfect a market, ransacked the place and attacked the vehicles of sanitation workers. About two dozen people were injured, and a local curfew had to be imposed.

Fear is one of the biggest challenges to containing this outbreak. The disease is seen as a death sentence even though about half survive, and getting good treatment early can improve the odds considerably.

Many who do survive struggle to convince family and friends they're no longer contagious. Doctors are trying to help, holding ceremonies and publicly embracing patients when they are discharged to show that contact is safe.

Officials in Liberia planned just such ceremony Saturday for two health care workers who have recovered after receiving ZMapp, the same experimental drug that two Americans also received before they were treated and released in the United States.