The Asterisk

10.31.14 9:45 AM ET

The WHO’s Big Asterisk on Liberia’s Ebola Case Decrease

WHO officials say they’re seeing a decrease in cases in Liberia—but that’s because no one can say how many newly infected people they haven’t been able to count.

Actual cases of Ebola in Liberia, according the World Health Organization, are decreasing. This statement, interpreted by many in the media as a sign that the epidemic is abating, prompts more questions than answers.

The first indication of this confusion can be found in the audio clip in which Dr. Bruce Aylward, the WHO’s assistant director-general, announced the decrease Wednesday. “I am terrified that the information will be misinterpreted and people will start to think, ‘Oh, great, this is under control,’” he told reporters at the Geneva media briefing, after announcing the decrease. “That’s like saying your pet tiger is under control. This is a very, very dangerous disease.”

Somewhere in the near-daily updates from the WHO on Ebola numbers in West Africa, we’ve forgotten the disclaimer that accompanies all of them: These numbers are not indicators, not evidence. They are the best approximations we have for analyzing the scale of this epidemic but they are, by nature of human error combined with the difficult of tracking an epidemic in rural West Africa, flawed. By no means enough to make conclusions about whether or not the epidemic in Liberia, or in the rest of West Africa for that matter, is waning. They are the result of human surveillance performed by inundated governments that lack the money, technology, and manpower to do it well.

If the WHO has done one thing right in this epidemic, it’s repeatedly remind those on the receiving end of the numbers that they are merely estimates. If the receivers have done one thing wrong, it is to ignore that statement.

“The sense down there is we have to understand what [this decrease] is,” WHO spokesman Tarik Jasarevic tells The Daily Beast. Jasarevic says that while the tendency is to think that fewer cases means the epidemic has slowed, he brings up the possibility that the decrease in numbers is instead a reflection of fewer people in Liberia going to treatment centers. Perhaps people still see it as a simply a place to die, he says, or they want their loved ones to be buried properly. Perhaps instead, he then adds, it is a reflection that an increase in support is working.

The point is: It’s too early for optimism. “Even if this is real, it could be just a decrease and we could see it increase again. We are trying not to be too optimistic in declaring victory because we still don’t really know,” says Jasarevic. When asked about the news coverage that followed the Geneva press conference, he dismisses it saying people will “interpret things however they want.” In his mind, this is only as problematic as the decrease in international support that it may cause. “We need to keep working. People should not think it’s over.”

At the WHO press conference in Geneva, several reporters pushed Aylward to discuss why the death toll still stands at just under 5,000 people—where it has remained for weeks. When one particularly eager reporter asked if the number of deaths had gone down, he nearly laughed in surprise. “No, they have not gone down.” Aylward didn’t answer why the death toll has not risen concurrently with the number of cases (which now stand at more than 13,000)—instead, he reaffirmed that the mortality rate for the epidemic stands at 70 percent in Liberia, Sierra Leone, and Guinea.

Using those numbers, the death toll may be closer to 9,100. While Jasarevic confirms that, using the morality rate, the death toll may be as much as twice as high (“exactly”), he exercises caution. “I don’t want to go into that, it’s a guessing thing,” he says. “We know there are people unaccounted for. We don’t know how many.”

If there is one thing his organization can’t be criticized for, it’s how many times they have asserted that the inaccuracies in reporting exist. “These shocking figures are vast underestimates,” the organization’s director, Margaret Chan, told the United Nations at an emergency meeting on Sept. 18th, when the cases stood just above 5,000 and the deaths at nearly half that.

Ruwan Ratnayake, an epidemiology technical adviser for the International Rescue Committee, has extensive experience tracking epidemics of this nature. “I agree there is an underreporting of cases. Any way you slice it, you’re going to have underreporting pretty extensively,” he says. “WHO has been consistently saying is that there is underreporting. There are many links in the system where we can miss cases—that’s not trademark of Ebola, it’s a trademark of surveillance. It’s not always going to be perfect.”

In Ratnayake’s thinking, the reporting problems stem from surveillance and the other determinants of transmission in West Africa. “Cases may be hidden by communities, cases may be happening in areas that are remote and far off mountainous areas,” he says. “There are regions in Sierre Leone and Liberia that are very much cut off from communication, so that becomes a feature of surveillance.”

Ratnayake says these factors can also play into the New York Times report that some treatment centers in Liberia have empty beds. “I think in epidemiology we are always careful to talk about causation X caused Y. I don’t think we know yet why the beds are not full.” While governmental organizations and NGOs have tried to build treatment centers near outbreak hotspots, he says the nature of the fast-moving epidemic could make those locations irrelevant quickly—their location could answer the question as to why they’re empty. “These pieces of evidence are key. Are we not getting people into beds or do these people not exist?” he asks.

While Ranayake echoes the WHO’s claim that it is too soon to tell, he’s also keenly aware of potential implications of the decrease. “In surveillance you’re always worried about those areas that are too quiet,” he says. “Because you wonder if those areas are so remote and far off and we might not know what’s going on there.”

Around Liberia, opinions as to whether the epidemic is slowing vary. Sam Bropleh, a first responder near Monrovia, told All Africa news that he’s seen things slow down. “I took three cases today at the Island Clinic. To be frank, the cases are decreasing on a daily basis,” he said. “The way the cases were and the way calls were coming in before; everything has dropped. From now to the end of November, I can tell you, things will be fine.” But officials with Doctors Without Borders/Médecins Sans Frontières spoke out against assertions that the epidemic there is slowing down. “It is too soon to draw conclusions on the reduction of Ebola cases in Monrovia,” said Fasil Tezera, the head the NGO’s Liberian mission in a statement, adding “While the number of admissions in MSF’s 250-bed Monrovia Ebola center have dropped to around 80, we do not have a full picture of the extent of the outbreak and estimates might not be reliable.”

We don’t know with any sort of certainty how many people are infected with Ebola in West Africa. We know with even less how many have died. Uncertainty is uncomfortable, but in a situation that threatens the security of the world, it’s arguably necessary. Celebrating an apparent fall in numbers in Liberia in the absence of even the slightest confirmation as to why is not only uninformed—it’s misleading.