As the Ebola epidemic unfolds, underreporting appears to be getting worse.
In August, the World Health Organization said that the reported Ebola numbers “vastly underestimate” the epidemic’s magnitude. WHO’s situation updates frequently point out gaps in the data.
A fall in the rate of increase in official Liberia numbers reflects a deterioration in the ability of overwhelmed responders to record accurate epidemiological data.
Getting the numbers right is hard for many reasons.
* Many patients don’t seek medical care
* Of Ebola people who die at home, some are buried without ever coming to officials’ attention.
* Testing is a big problem as well because of lack of capacity and other reasons
Methodology and Risks of Accurate Counting
In a technique called capture-recapture, epidemiologists visit one area or district and determine what percentage of the Ebola cases and deaths there has found its way into official records. “You throw out the net twice, and you compare,” says Martin Meltzer of the Centers for Disease Control and Prevention (CDC) in Atlanta, who is modeling the Ebola epidemic. (The term capture-recapture was borrowed from researchers who study the size of wildlife populations using two rounds of trapping.) But this method is logistically challenging and possibly dangerous, given the hostilities that some Ebola response teams have met, Meltzer says: “I’m not going to ask people to risk their lives to collect some data.”
[NBF – Clearly the statistical estimates are showing somewhere between 2.0 to 2.5 — and at most 3.0 times undercounting of cases and deaths. Clearly the situation is that the response is inadequate. There is no reason to risk lives to try to get more accuracy in the second decimal point of the estimate.]
CDC has a computer model that, among other things, calculates how many hospital beds should be in use at any given time based on the cumulative number of cases at that moment. For 28 August, the time the paper was written, that number was 143 beds for Liberia; but people in the field told Meltzer that the actual number of beds in use was 320, a factor of 2.24 higher. (These numbers can be found in an annex to the paper.) “We had heard some other numbers that were higher, so we rounded that up to a correction factor of 2.5,” Meltzer says. But it’s a very rough approximation. Also, underreporting is likely to vary greatly from one place to another and over time, he says.
What Good News is There
* there has been an increase in safe burials
* The number of new cases in some areas at the epicenter of the outbreak—Kenema and Kailahun districts in Sierra Leone and Liberia’s Lofa County—has been dropping, and that’s not a result of underreporting
SOURCES- ScienceInsider, Guardian UK, BBC News