Every couple of days, the World Health Organization (WHO) issues a “situation update” on the Ebola epidemic, with new numbers of cases and deaths for each of the affected countries. These numbers―9216 and 4555 respectively, according to Friday’s update―are instantly reported and tweeted around the world. They’re also quickly translated into ever-more frightening graphics by people who follow the epidemic closely, such as virologist Ian Mackay of the University of Queensland and Maia Majunder, a PhD student at MIT who visualizes the data on her website and publishes projections on HealthMap, an online information system for outbreaks.
But it’s widely known that the real situation is much worse than the numbers show because many cases don't make it into the official statistics. Underreporting occurs in every disease outbreak anywhere, but keeping track of Ebola in Guinea, Liberia, and Sierra Leone has been particularly difficult. And the epidemic unfolds, underreporting appears to be getting worse. (“It’s a mess,” says Mackay.)
So what do the WHO numbers really mean--and how can researchers estimate the actual number of victims? Here are answers to some key questions.
Does WHO acknowledge that the numbers are too low?
Absolutely. In August, it said that the reported numbers "vastly underestimate" the epidemic's magnitude. WHO’s situation updates frequently point out gaps in the data. The 8 October update, for instance, noted that there had been a fall in cases in Liberia the previous 3 weeks, but this was “unlikely to be genuine,” the report said. “Rather, it reflects a deterioration in the ability of overwhelmed responders to record accurate epidemiological data. It is clear from field reports and first responders that [Ebola] cases are being under-reported from several key locations, and laboratory data that have not yet been integrated into official...Continue Reading »