IT was an eerie encounter.

Barely minutes after stepping off our Kenya Airways flight from Nairobi at South Sudan's Juba International Airport, all passengers were ushered towards a large white marquee tent that sat adjacent to the arrivals hall.

As the tent flap was pushed back, the scene inside initially resembled something from a high-tech science-fiction film. On closer scrutiny, though, the all-enveloping masks, suits, aprons and rubber boots of the South Sudanese Red Cross workers that confronted us were nothing more than the most rudimentary of protective measures against the disease for which we were about to be screened - ebola.

Having had our temperatures gauged by a gun-like scanner held to our forehead, we were duly allowed to enter the country with a certificate confirming our "clean screening".

I had arrived in South Sudan to cover an altogether different story, the pressing humanitarian crisis there that has worsened as a result of the civil war gripping parts of the country. Ebola was the last thing on my mind.

Although outbreaks of the deadly virus have occurred here in East Africa in the past, the current ebola contagion that has killed more than 2600 people and infected some 5300 more has largely been confined to West African nations like Sierra Leone, Liberia, Guinea, Nigeria and Senegal.

The ebola virus, which cannot be cured but can be treated, can kill up to 90% of those who catch it and attacks the organs and leads to fever, diarrhoea, bleeding and, in most cases, death.

A few days ago, the World Health Organisation (WHO) announced that this, the worst ebola outbreak in history, was showing no signs of slowing. Indeed, the epidemic in West Africa, according to experts, is rapidly outpacing the international efforts to contain it.

In the last week alone there have been 700 new cases reported. So pressing is the threat that the United Nations has described it as the "greatest peacetime challenge" in its history.

"As the disease spreads, a truth becomes clear. None of us is insulated from the threat of ebola. All of us must be part of the response," Secretary-General Ban Ki-moon told the UN General Assembly on Friday.

Last week too, the 15-nation UN Security Council unanimously adopted a resolution declaring the ebola virus a threat to international peace and security. The resolution was co-sponsored by 131 countries, the largest official show of international support for a Security Council resolution in history, according to the United States.

Almost daily the scale and severity of the epidemic is making headlines, even if six months into its grip on Africa the West only now seems to be waking up to the threat.

Already, the United States plans to send 3000 military personnel to the region and on Friday, eight members of a team trying to raise awareness about ebola were hacked to death by villagers in Guinea using machetes and clubs. This last gruesome incident was yet another sign of the suspicion many people in parts of rural West Africa feel towards official attempts to combat the disease.

This weekend, streets in Freetown the capital of Sierra Leone were deserted as the West African state began a contested, three-day lockdown in a bid to halt the spread of the disease.

Sierra Leone president, Ernest Bai Koroma, urged people to heed the emergency measures as health workers, some clad in protective biohazard suits, went house to house, checking on residents and marking each doorway they visited with chalk.

Radio stations played ebola awareness jingles on repeat and encouraged residents to stay indoors.

"As they are fighting this ebola, we pray that it will be eradicated. That's what we are praying for," said resident Mariam Bangura as she waited at her home in Freetown's west end neighbourhood. Many residents were limited to looking out over this normally bustling seaside city from windows and balconies.

Nearly 30,000 health workers, volunteers and teachers aim to visit every household in the country of six million people by today to educate them about the disease and isolate the sick.

In Freetown, teams got off to a slow start, waiting several hours to receive kits containing soap, stickers and flyers.

A few police cars and ambulances, sirens blaring, were reported to be the only traffic on the otherwise empty streets.

In Sierra Leone alone, at least 562 people have died so far from the disease.

"Today, the life of everyone is at stake, but we will get over this difficulty if we all do what we have been asked to do," Koroma said in a television address late on Thursday. "These are extraordinary times and extraordinary times require extraordinary measures."

Some have questioned whether the campaign will be effective. Sierra Leone newspaper Awareness Times, in an editorial, called the preparations for the lockdown "chaotic" and recommended its postponement.

"This morning many families are calling on the radio crying because of lack of food in their homes," said Ahmed Nanoh, executive secretary of Sierra Leone's chamber of agriculture. "Food prices have gone up 30%. Many homes that cannot afford food are starving.

Medical charity Médecins Sans Frontières, which has been at the forefront of the effort to contain the epidemic, warned last week that the lockdown could lead to the concealment of cases, potentially causing the disease to spread further.

An official for the United Nations children's agency Unicef, Roeland Monasch, said, however, that the "Ose to Ose" campaign, which means "house to house" in local Krio, would be helpful.

"If people don't have access to the right information, we need to bring life-saving messages to them, where they live, at their doorsteps," he said.

In parts of West Africa, healthcare workers seeking to contain the ebola outbreak have often been met with deep mistrust, hampering their efforts to stop its spread. The eight-person team working in a remote part of southeastern Guinea a few days ago were the latest victims, their bodies apparently dumped in a village latrine.

People in Liberia tell of an incident some months ago when citizens of the town attacked a community health team which came to spray the area with chlorine, a cheap and effective way of killing ebola, and tried to set its car on fire. Now a lone pink plastic bucket containing chlorinated water sits in the middle of the town, intended for people to use to wash their hands. No-one touches it. In many parts of West Africa, people view or explain away events in their lives through superstition and religious or local customs. Many simply believe that ebola does not exist.

In Liberia, people have been known to fight hospital staff to retrieve bodies of family members who have died. This despite the fact that touching the deceased is extremely dangerous, given the virus's contagiousness.

Attacks, too, like the one over the last few days in Guinea are not uncommon and similar misguided reactions to the disease can be found across this part of West Africa.

Some months ago in Sierra Leone's Freetown, thousands marched at an ebola treatment centre following allegations by a former nurse that the deadly virus was invented to conceal "cannibalistic rituals" at the facility, a regional police chief told reporters.

The lack of staff, equipment, facilities and public understanding of how ebola is transmitted has contributed to the disease's continuing spread. These key issues will be the focus of a US humanitarian mission to West Africa.

America's response is the first by a government on a large scale. Until now the burden has been carried by charities such as Médecins Sans Frontières (MSF), which has 2000 staff in the affected countries.

On Sepember 16, US President Barack Obama announced his plan for Operation United Assistance, which he says will deploy 3000 military engineers, medical personnel and other troops in the region. US troops will serve as an "air bridge" to transport doctors, nurses, medical supplies, and clinics into the hardest-hit areas. In all, the United States has committed more than $175 million to the effort, a figure officials said could rise.

The operation will amount to the largest humanitarian commitment since the American response to the 2004 earthquake and tsunami in Aceh, Indonesia.

Over this weekend, 45 more US soldiers are scheduled to arrive in Liberia's capital Monrovia to begin setting up a command centre, Department of Defence spokesman Rear Admiral John Kirby confirmed on Friday.

In a dramatic increase in the global response, largely focused on Sierra Leone, the Cuban government is sending 165 health professionals to that country. China is deploying 59 health workers while the UK Government has promised to construct a 62-bed hospital in the country's capital.

British NHS staff are being encouraged to volunteer to help with the outbreak. The Department of Health's chief medical officer Professor Dame Sally Davies has written to health service staff to point them towards the UK International Emergency Medical Register.

Two things are urgently needed. The first is the rapid provision of basic, cheap protective gear such as gloves, gowns, surgical masks and disinfectant. Domestic health systems in affected countries have crumbled as nurses and doctors have fallen ill or died for lack of these basic items.

Any response, of course, will ultimately succeed - or fail - based on the pace of execution in getting these much-needed resources on the ground.

Certain experts say all of this is too little, too late to effectively halt a spread of the disease. Some medical analysts have concluded that if the stated rate of growth is correct and the estimate of infections is correct then there will be 80,000 infections by the end of this year.

What is not in doubt is that ebola is now growing exponentially, with the number of new cases roughly doubling every three weeks or so. And certainly the longer ebola is allowed to replicate in humans, the greater the risk that it will become more contagious. In Monrovia, Liberia's capital, it is thought to be doubling every two weeks.

For now the disease is spreading out of control in Guinea, Liberia and Sierra Leone, with spillover into West Africa's powerhouses, Senegal and Nigeria.

Six weeks ago, the Council on Foreign Relations' John Campbell, former ambassador to Nigeria, warned that the spread of ebola inside Nigeria, particularly in Lagos, the capital with a population of approximately 22 million, would put the world's epidemic into completely uncharted territory.

This weekend Freetown, Sierra Leone's capital remains in lockdown. Elsewhere in West Africa, efforts to stop the disease moving to other parts of the African continent are also being beefed up. Coming through East Africa's Nairobi airport while going to and from South Sudan recently, it was impossible to avoid the ebola warning posters that covered the walls in this an air hub through which tens of thousands of passengers transit from all across Africa. After a long and some say dangerous delay, the race is now on to halt ebola's deadly advance.

As Médecins Sans Frontières has said: "Speed is of the essence. We do not have months or even weeks to wait. Thousands of lives are at stake."