There’s a risk to putting too much stock in the estimates coming out of Ebola-affected countries.
We know the Ebola outbreak in West Africa is really bad. But exactly how bad remains largely a mystery.
There have been 15,351 reported Ebola cases and 5,459 reported deaths, according to the most recent estimates released by the World Health Organization on Nov. 21. The vast majority of these are concentrated in Liberia, Sierra Leone, and Guinea.
But the numbers are ballpark figures, based on reports from the affected countries. While they provide important information about the trajectory of the epidemic and how response efforts are working, officials warn that the totals are likely pretty far off base.
And there’s a real danger in relying too heavily on these shifting figures: Prematurely altering response strategy based on some recent positive signs can wipe out progress that has been made in containing the epidemic.
“The numbers we’re using for Ebola cases are the best numbers we have from health ministries and Ebola treatment centers working on the ground, but they do go through revisions and often change,” said WHO spokesman Daniel Epstein. “We’re doing our best to refine the data and get it as accurate as we can, but there’s not always 100 percent accuracy.”
The discrepancy between total reported and confirmed cases can be as high as a few thousand. In Liberia, there have been 7,082 reported Ebola cases, according to WHO, only 2,669 of which are confirmed. In Sierra Leone, there have been 6,190 reported cases and 5,152 confirmed, and in Guinea, there have been 2,047 cases and 1,745 confirmed.
Ebola cases can be confirmed only through laboratory tests, which are not available in many regions of West Africa. The numbers reported could include deaths that were incorrectly attributed to Ebola, Epstein said, and totals may be revised downward if the cause of death is confirmed to be something else. However, a more serious problem is the underre-porting of cases that actually are Ebola.
WHO officials think there could be thousands more cases that have not been reported.
“In some areas, we think real numbers are two times the numbers reported; in others it may be as high as 2.5 times and others more like 1.5,” Margaret Harris, a WHO spokeswoman in Sierra Leone, wrote in an email. “This varies not only by country but by district. For instance, where there are no laboratories and cases are in very remote areas, it stands to reason there are many cases and deaths going unreported.”
The misunderstanding and fear surrounding the virus makes underreporting a significant problem. Officials on the ground say many people are remaining at home after becoming sick, afraid of the treatment centers or of the stigma associated with the disease. This can result in the infection of family members and neighbors, continuing the chain of transmission.
“We still have anecdotal information that some communities are denying the fact that there is Ebola,” Pieter Desloovere, a WHO spokesman in Liberia, wrote in an email. “In addition, some communities also hide their sick family members at home and do not want to send them to a health facility for treatment out of fear that the person will die. All these cases are not reported and are not part of the statistics.”
This can be particularly true in remote areas, where there may be fewer resources and less of a grasp on the extent of the situation.
“Cases are down in Monrovia, [but] these West African countries have one big port city, outside it’s the jungle, like the Heart of Darkness,” said David Morens, senior adviser to the director of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health. “We don’t have anywhere near a handle on [the situation in these areas]. There’s almost nothing out there.... The epidemic will move place to place.”
“Case-finding teams” are going into these more remote villages to actively search for sick individuals, Epstein said. The crews are doing regular check-ins several times per week across the three most hard-hit countries, urging residents to bring out any sick people and looking for any who may have died unreported.
Several agencies, including the ministries of health, the Centers for Disease Control and Prevention, USAID, and Doctors Without Borders, are working on data collection, trying to integrate findings so everyone is using the same information, Epstein said.
But there is a lot of ground to cover, and limited personnel.
More important than the exact number of cases, health officials say, are the broader trend lines, and in some areas there are definite signs of improvement. The CDC and WHO have said cases are no longer rising exponentially in Liberia, and there are indications that response efforts in the country are making real progress.
But this has happened before. Officials say infections have come in waves during the Ebola epidemic, and they cite previous dips in case numbers that were then followed by spikes as a warning against premature optimism.
“In Liberia, back in March-April we also saw a drop in the number of cases, only to hike up again in August-September,” Desloovere wrote.
Meanwhile, infections are still rising rapidly in Sierra Leone and Guinea. The number of reported cases in Sierra Leone has increased 30 percent from three weeks ago to the most recent WHO report on Nov. 21. The number of reported cases has increased 18 percent in Guinea during that time, and 8.5 percent in Liberia.
A recent cluster of Ebola cases in Mali has officials concerned that the outbreak could expand in that country.
Health experts, government officials, and aid organizations on the ground are pleading with the public not to forget Ebola or dial back response efforts in light of some seemingly positive, but fragile, developments.
“We are seeing a very mixed picture right now,” Harris wrote. “The most dangerous conclusion we could make is to think that we’ve got it beaten in the areas where numbers seem to be down. What has happened too often during this epidemic is that just when case numbers had dropped considerably, an unsafe burial or an infected person whose fear of quarantine has driven them to hide their illness might spark a whole new chain of transmission. If the outbreak response has ‘moved on,’ that is, the surveillance teams, labs and treatment centres are no longer active in that area, the new chain of transmission can turn into a full on raging outbreak before we have time to stamp it out.”