The current outbreak of Ebola virus disease, which can produce bleeding in sufferers and is capable of killing a large proportion of those who catch it, started in the west African nation of Guinea in December last year. It then spread to neighbouring Liberia and Sierra Leone. Since the end of May, there has been an alarming surge in cases and deaths.

The World Health Organization is convening a meeting this week of an emergency committee to decide whether the current situation constitutes a ‘Public Health Emergency of International Concern’ (PHEIC). Under WHO’s International Health Regulations, a PHEIC is defined as “an extraordinary event which is determined to constitute a public health risk to other States through the international spread of disease and to potentially require a coordinated international response.”

With over 1,600 cases and nearly 890 deaths, the present epidemic is already almost four times larger then the next biggest one, which occurred in Uganda in 2000. Up to now, the current epidemic has been largely confined to Guinea, Liberia and Sierra Leone.

However, a Liberian government official, who took a flight to Nigeria and died there, turned out to having had the disease. A doctor who treated the man as well as two other Nigerians appear to have caught the virus.

Two American missionaries, one of them a doctor, who were looking after Ebola patients in Liberia and themselves became infected, have been flown back to the U.S. for medical care.

Meanwhile, there are reports from Morocco that an air traveller from Liberia who died there had the disease.

A Saudi man has, on his return from Sierra Leone, been admitted to a hospital in the city of Jeddah with symptoms of the disease.

There are five species of Ebolavirus, four of which cause disease in humans. The one responsible for the ongoing outbreak in West Africa is the Zaire ebolavirus, which has the highest case-fatality rate (about 60 per cent to 90 per cent).

There is, at present, no approved vaccine or drug for the disease.

The first Ebolavirus outbreaks occurred simultaneously in 1976 in the Democratic Republic of Congo and Sudan. Since then, there have been over a score of outbreaks, all of them in Africa. Fruit bats are believed to be the natural host for the virus.

“Despite the frequently promulgated image of Ebola virus mysteriously and randomly emerging from the forest, the sites of attack are far from random,” observed Daniel G. Bausch, a tropical infectious diseases expert with the Tulane University School of Public Health and Tropical Medicine in the U.S., and Lara Schwarz in a recent editorial in PLOS Neglected Tropical Diseases.

Rather, such large haemorrhagic fever virus outbreaks almost invariably occurred in areas where the economy and public health system had been decimated by years of civil conflict or failed development, they pointed out.