BACK in 1998, while covering the impact of a major earthquake in Afghanistan's northern Takhar Province, I interviewed a doctor from an international medical aid agency.

Already under tremendous pressure, the doctor broke off mid-sentence to answer a radio call from a colleague working in a remote district nearby.

In that area, people displaced by the quake had died from a disease that until that moment had not been identified.

"That's all we need," said the doctor, turning back to me after finishing the call. In the continuing interview she said that her colleague had just confirmed an outbreak of the deadly Crimean-Congo haemorrhagic fever (CCHF) that would subsequently result in 19 cases and 12 fatalities.

The disease is just one of a group of viral haemorrhagic fevers of which Ebola virus disease (formerly known as Ebola haemorrhagic fever) is perhaps the best known.

Ebola is once again in the news after Sierra Leone, a former British colony, declared a state of emergency yesterday, joining Liberia in imposing tough controls to curb the worst ever outbreak of the virus amid fears it could spread beyond west Africa.

Sierra Leone President Ernest Bai Koroma is due to meet with leaders of Liberia and Guinea in Conakry today to discuss the epidemic and said he was cancelling a visit to Washington for a US-Africa summit next week.

"Sierra Leone is in a great fight ... failure is not an option," Mr Koroma said in a speech earlier this week, adding that the state of emergency would initially last between 60 and 90 days. "Extraordinary challenges require extraordinary measures."

In a measure of rising international concern, the UK too held a government meeting on Ebola, which it said was a threat it needed to respond to.

Ebola is the stuff of nightmares, a biological doomsday mechanism. The virus punches microscopic holes in the lining of blood veins, vessels and capillaries. Within hours, these punctures enlarge, filling the bowels, and respiratory channels. Patients feel immense pain and suffer hallucinations, their tears literally dripping red with blood.

The process of infection, usually through infected bodily fluids, through to death can be as rapid as five days.

Already the virus has been blamed for 672 deaths in Liberia, Guinea and Sierra Leone, according to the World Health Organisation (WHO). It has also reached Nigeria's biggest city Lagos, where authorities confirmed that a man had died of the virus.

While it can kill up to 90 per cent of those who catch it, the overall death rate in West African countries currently affected is around 60 per cent.

Like crime or terrorism, diseases like Ebola present transnational security threats. In an era of globalisation, infectious diseases have experienced something of a resurgence. Migration, urban crowding, overuse of antibiotics and changing sexual behaviour are just a few factors that have contributed to this.

What then does the current Ebola outbreak tell us about global health and security preparedness set up to tackle such dangers?

Since 1976, when scientists first identified the Ebola virus, some 2,200 cases have been confirmed in outbreaks spread across equatorial Africa. These include Congo, the Democratic Republic of the Congo, Uganda, Gabon, Sudan and what is now South Sudan. The most recent major outbreaks prior to the current one were in Uganda and the Democratic Republic of the Congo in 2012.

Although it is unprecedented in West Africa, the start of the current outbreak followed the pattern of past ones in central Africa.

What all these countries have in common are porous borders that provide little barrier to the spread of the disease. The West African region too shares a vast tropical rainforest rife with virus-harbouring animals, including rodents, bats, and chimpanzees.

Public health workers point to the fact the latest outbreak has hit three countries and their urban centres simultaneously, a first in history, and is most likely a result of frontiers' easily and regularly crossed.

Officials say that in such regions it is not uncommon for members of the same family living on different sides of a border to visit each other, while other people border-hop to engage in business and commerce. Already the present epidemic has officially been declared a regional threat.

Last Friday a case was confirmed in Nigeria, Africa's most populous nation, after a Liberian man collapsed at Lagos airport and later died.

Patrick Sawyer, the first recorded case of Ebola in Nigeria, took a flight that stopped in Ghana and Togo, raising questions over how a person whose sister had died of the disease three weeks before was able to board an international flight.

Yesterday, in response, Ghana said it was immediately introducing body temperature screening of all travellers from West African countries at Accra airport and other major entry points, with isolation centres being set up in three towns.

According to Kyei Faried, deputy director in charge of disease control in the country, the Ghanaian authorities had a list of 11 passengers who disembarked from Mr Sawyer's flight and were monitoring them.

Back in Mr Sawyer's home country of Liberia, where seven of 15 counties have identified cases of the virus, moves have been made to restrict public gatherings, shut many border crossings and open testing centres. If the outbreak continues, governments could institute even tighter border controls and travel restrictions.

Part of the problem all these authorities face is that a carrier of Ebola could theoretically carry the disease during the incubation period, which ranges from two to 21 days.

Those who know about the disease say that, despite the vast sums of money in research on vaccines and treatments, Ebola remains best tackled today in much the same way it was during its first epidemic in 1976. Far from the high-tech nuclear, biological and chemical "Noddy suit", and vast mobile laboratories, it is soap, antiseptics, clean water, basic protective gear and quarantine that remain the main weapons of any response.

According to Laurie Garrett, a senior fellow for global health at the Council on Foreign Relations, after 9/11 and the 2001 anthrax attacks the US Congress ordered the US Centres for Disease Control and Prevention to designate a list of possible bioterrorist germs, and under Project BioShield financed research and development on treatments and cures.

Ebola alone saw $5.4 million in funds allocated to tackle the disease, even though many of the treatments formulated "never left the lab bench".

Back in 2000 the UN Security Council unanimously adopted Resolution 1308 identifying HIV as a threat to international peace and security.

Like the HIV/Aids pandemic in Africa, Ebola also represents a security risk due to the transnational and destabilising impact it can have on the economies, food production and political order of the poorest countries. The battle to halt its spread has never been more pressing.