Under-reporting of measles: an evaluation based on data from north rhine-westphalia

Eliminating measles in Europe by 2015 is a WHO health goal. In Germany, physicians are legally required to report measles cases, yet it seems likely that reporting is less than universal. The goal of this study is to compare the number of measles cases that are reflected by data from the statutory health insurance (SHI) carriers with the number of physician-reported cases during and after a recent outbreak in the German state of North Rhine-Westphalia (NRW).

We analyzed the billing data of SHI carriers relating to measles in 2006 and 2007, as well as the measles cases that were reported in NRW over this period as required by law. We calculated the incidence of measles as the number of measles cases per 100 000 insurees (SHI carrier data) or per 100 000 persons in the overall population (reporting data).

The measles outbreak in the first half of 2006 comprised 1713 measles cases according to the SHI data and 1665 cases that were reported as required by law (ratio, 1.02:1). From mid-2006 to the end of 2007, the SHI data reflected 821 cases, but only 349 cases were reported (ratio, 2.35:1). Younger patients were more commonly found among the cases reflected in the SHI data than among the reported cases.

Our study confirms that the system of legally mandated reporting underestimates the true number of measles cases, particularly in times when most cases are sporadic, and particularly in children who are less than 5 years old.