For the experts who prepare for the world’s humanitarian disasters, the alarm bells began ringing when the graph of Ebola cases stopped showing a simple linear increase and abruptly shot upward into an exponential curve, accelerating at a sharply faster rate with no end in sight.

That moment arrived this month. After building steadily since March, the number of Ebola cases shockingly doubled in just three weeks. It triggered the announcement on Tuesday of a major U.S. military operation in West Africa, including 3,000 U.S. troops and the creation of a new Pentagon command in Liberia to set up Ebola treatment centres and train hundreds of health workers.

The World Health Organization reported on Tuesday that the number of Ebola cases in West Africa has climbed to nearly 5,000. The death toll has similarly risen exponentially, reaching nearly 2,500 deaths. The biggest worry is the dramatic jump in the past 21 days, showing a much faster rise in the epidemic.

“It’s spiralling out of control,” U.S. President Barack Obama warned, predicting that the number of Ebola cases could even climb into the “hundreds of thousands” if nothing is done. The panic could lead to a breakdown of several West African economies and a “potential threat to global security,” he said.

One recent academic analysis projected that Ebola cases could reach 277,000 by the end of this year in the worst-case scenario if nothing is done to halt the rise, although United Nations officials are hoping to limit the number to something in the tens of thousands.

“Quite frankly, this health crisis we face is unparalleled in modern times,” said Bruce Aylward, assistant director-general of WHO, at a news conference in Geneva on Tuesday.

“We risk a humanitarian catastrophe if we do not see rapid action,” he said. “You start to get a sense of the rapid escalation now of the virus as it moves from what was a linear increase to an exponential increase.”

Earlier this month, the WHO shocked observers by saying it needed to prepare for up to 20,000 cases of Ebola. “That seemed like a lot,” Mr. Aylward said. “That does not seem like a lot today, let’s put it that way. The reality here is we don’t know where the numbers are going.”

He acknowledged that some projections soon could mention the possibility of up to a million Ebola cases. With the “massive surge” of U.S. troops, along with health workers from other countries, “the numbers can be kept in the tens of thousands,” he said. “But that is going to require a much faster escalation of the response, if we’re going to beat the escalation of the virus.”

The United Nations Security Council is holding an emergency session on Thursday to discuss the Ebola crisis. A month ago, UN officials said $100-million (U.S.) would be needed to respond to the crisis. Now they are saying that $1-billion is needed. Less than a third of this target has been raised so far.

“Our ask has gone up 10 times in a month, and the reason is that the outbreak in the past month has doubled in size, and we realize it will go on doubling in that sort of frequency if we don’t deal with it,” said Dr. David Nabarro, the UN senior co-ordinator for Ebola.

“It’s accelerating as it goes through time, that’s the frightening thing, and that’s why we’re going to have to do something quite exceptional,” he said.

The epidemic has reached the point where hospitals and clinics in Liberia are completely full, forcing Ebola victims to wander nomadically through city streets, searching in vain for any place to accept them, while they fall sicker and weaker.

Those scenes are “absolutely gut-wrenching,” Mr. Obama said on Tuesday in his most strongly worded comments on the Ebola crisis so far. “These men and women and children are just sitting, waiting to die,” he said. “And it doesn’t have to be this way.”

The crisis will get worse before it gets better, he said. “But right now, the world still has an opportunity to save countless lives. …We can’t dawdle on this one.”

Mr. Obama, who has faced criticism for failing to take stronger and faster action on the Ebola crisis, made his remarks during a visit to the Centers for Disease Control and Prevention in Atlanta.

The Ebola outbreak began early this year in Guinea and quickly moved into Liberia and Sierra Leone, with a few cases also spreading to Nigeria and Senegal. The crisis has been obvious since July, when the desperate shortage of hospital beds was already clear.

After an agonizingly slow start, the world is finally beginning to move more dramatically on the Ebola crisis. Hundreds of health workers are now being sent to West Africa from countries ranging from China and Cuba to Britain and France.

One of the biggest dangers of the Ebola crisis is its devastating impact on the health-care systems of some of Africa’s poorest countries. Hundreds of health workers have been sickened or killed by Ebola, and the epidemic has drained resources from other diseases.

“We must prevent the complete collapse of health systems in the affected countries,” said Valerie Amos, the UN under-secretary-general for humanitarian affairs.

“Already it’s estimated that more people have died from secondary aspects – from malaria, tuberculosis or in childbirth, or from chronic aspects – than have died from Ebola.”

JOHANNESBURG — The Globe and Mail
Published Tuesday, Sep. 16 2014, 8:42 PM EDT
Last updated Tuesday, Sep. 16 2014, 10:29 PM EDT