Willam Pooley, 29, British citizen who contracted the deadly Ebola virus while working as a volunteer nurse in Sierra Leone, one the countries that has been hit by the worst outbreak of the disease, has been cured after being  treated by the experimental drug ZMapp.

While this is great news, Ebola, which has already killed more than half of the 3,000 people diagnosed with the virus, is feared could kill up to 20,000 people across West Africa who have no hope of ever getting the experimental drug.

ZMapp has been used to treat seven other patients, including two American aid workers who got cured, but not all have been lucky to survive. A top Liberian doctor  and another patient died in August despite receiving the ‘wonder drug’. The other five walked home safe and sound.

“I was very lucky in several ways; firstly in the standard of care I received, which is a world apart from what people are receiving in West Africa at the moment,” Pooley told the BBC News.

“And my symptoms never progressed to the worst stage of the disease, I’ve seen people dying horrible deaths, I had some unpleasant symptoms, but nothing compared to the worst of the disease.”

The Ebola virus, which is spread through contact with the bodily fluids of infected patients, was first detected in Guinea in March. It then spread to Liberia, Sierra Leone, Nigeria and Senegal, where at least one patient has been identified.

Nigeria,  the most populous nation in Africa, has already reported 19 cases and four deaths, most of them linked to a single traveler who flew to the commercial center, Lagos, from Liberia.

Local authorities managed to trace most of the people that come into contact with the man, but one of the contacts escaped from quarantine and fled to Port Harcourt, where it is suspected that more people could have been infected, Nigerian Health Minister Onyebuchi Chukwu said.

If this is confirmed to be true, it could easily become another viral spread of the diseases as witnessed in Liberia and Sierra Leone, where the countries’ poor health infrastructure have come under immense pressure from the Ebola outbreak.

The virus has taken a heavy toll on health workers in these countries, who account for more than 240 infected cases and more than 120 deaths.

“We are not being critical of our colleagues in west Africa. They suffer from a terrible lack of infrastructure and the sort of testing that everyone in our society takes for granted,” Bruce Ribner, medical director at Emory University Hospital in Atlanta  where the two American’s were treated told Scientific American.