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Worst case scenario is off the table, but where are Ebola numbers going?

11/20/2014 04:01 EST | Updated 01/20/2015 05:59 EST
TORONTO - The Ebola apocalypse scenario is off the table. But where exactly is this epidemic going?

Unfortunately no one is entirely sure. But those involved in charting the response feel certain that if the world eases up on efforts to quell the outbreak, the scenery won't be pretty when the journey ends.

Then again, it isn't pretty now. The latest counts from the World Health Organization suggest there have been 15,145 reported cases and 5,420 reported deaths. To put that in context, this epidemic has killed more than twice as many people as have been infected in all previous Ebola outbreaks combined.

Official counts are known to be an underestimate, though there is no real way of gauging how much higher true totals would be. The WHO thinks the real tallies may be double the counted cases. The U.S. Centers for Disease Control multiples the known numbers by two-and-a-half to come up with its estimates.

Either method produces a figure that is within the same area code as what the WHO had projected the outbreak count would be in early November — 21,000 cases. It is clearly not on track for what the CDC had warned might come to pass if more wasn't done to beat back transmission — between 550,000 and 1.4 million cases by late January.

Both organizations issued those prognostications in late September. And while the WHO was more conservative than the CDC when projecting how long the explosive growth in new cases might last, both agencies share a prediction in mid-November: This epic bout with Ebola is far from over.

"We know we can defeat this. Don't get me wrong. But we've still got a long way to go and we've got to keep the pressure on," says Martin Meltzer, a mathematical modeller with the CDC whose work focuses on infectious diseases.

"We can't let up with what we're doing now because it's still that big that it could flare up again."

Meltzer was the lead author on the CDC modelling study that suggested the Ebola case count could hit those stratospheric numbers by late January — and for just two of the three countries battling the outbreak, Sierra Leone and Liberia. (They felt the situation in Guinea was too unclear to offer a projection.)

At the time, the reported case count in Liberia was doubling every 15 to 20 days; in Sierra Leone, the numbers were doubling every 30 to 40 days.

On Wednesday, CDC Director Dr. Tom Frieden acknowledged for the first time publicly that his agency no longer feels that horrific projection is on the cards. Speaking to a hearing of a committee of the U.S. senate, Frieden did not replace the withdrawn numbers with more up-to-date estimates.

Infectious diseases expert Dr. Michael Osterholm is glad the CDC numbers are off the table, suggesting projections can take on a life of their own, shifting attention from the problem at hand — a truly disastrous ongoing outbreak — to why the modellers got it wrong.

He prefers simpler math to explain where the epidemic is going.

"There's going to be lots and lots of cases and lots and lots of deaths and this is a serious crisis," says Osterholm, who heads the Center for Infectious Diseases Research and Policy at the University of Minnesota

The WHO agrees.

Christopher Dye, director of strategy in Director General Margaret Chan's office, says the situation has changed a great deal from late August and early September, when the calculations released in late September were being draw up.

"We're not talking about anything like doubling (of cases) in three weeks or four weeks. It would be doubling in many months now. In other words, the whole thing has really slowed down," Dye says.

"But that is not a sign that the thing is under control."

The situation in Liberia, which in September was catastrophic, has improved. The increase in new cases there has slowed substantially, down to about 100 a week from 400 to 500 a week back then. Dye says the reason for the improvement isn't well understood. That for some makes the trend hard to trust, but still, people are grateful for the improvement.

On the other hand, Sierra Leone's situation has gone in the opposite direction, with sharp increases in some parts of the country, including the capital, Freetown. That situation is a source of much concern, and Dye says there's no way to project how long the trend will continue.

"It's possible Freetown could be a major-major disaster, instead of just a major disaster," he warns.

In Guinea, transmission persists, but the incidence — the increase in new cases — is no longer growing.

Dye says the relative stabilization of the situation has been a boost for people in the control program, confirming that while the dynamics of this outbreak are different — involving spread in densely populated urban centres and across porous borders — the virus responds to the control measures traditionally used to stop Ebola outbreaks.

"If the right things are done, district by district by district across the epidemic area, then this epidemic can be beaten," Dye says.

That means no letup in control efforts, he insists. "Even though the numbers may be flattening out in some places overall or even declining in Liberia, the response to that is not to slacken off at the moment."

Meltzer too warns that all it would take would be for people to loosen up on Ebola controls — returning to traditional burial rights, for instance — for transmission rates to explode again.

"At what point do communities say: 'We're tired of government taking away people in body bags. We want to have our traditional funerals again'?" he asks. "We don't know how long these lessons will stay embedded in people."

"Just to paraphrase Winston Churchill, this is definitely the end of the beginning, but it's not the beginning of the end."

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