Assessing the Impact of the 2009 H1N1 Influenza Pandemic on Reporting of Other Threats through the Early Warning and Response System

Published in the European scientific journal Eurosurveillance (Vol. 14, no. 45), this 3-page article explores a recent "notable surge in messages communicated through the Early Warning and Response System (EWRS) for the prevention and control of communicable diseases in the European Union". As detailed here, since the first cases of pandemic 2009 H1N1 influenza reported in the United States (US) on April 24 2009, the European Union (EU) Member States (MS), the European Commission (EC), and the European Centre for Disease Prevention and Control (ECDC) have relied heavily on EWRS to communicate messages related to the pandemic, with a significant increase in the number of messages posted on EWRS compared with the same period of the previous years.

In order to measure the impact of this increase on the reporting of other events, the researchers compared the messages posted in the EWRS since April 2009 with those posted in the previous years (2004-2008). For this study, EWRS activity was quantified using the term "new event", defined as an electronic message posted for all users by any user. New events were aggregated on monthly intervals from May 2004 through September 2009.

The analysis of the 65-month series, totalling 917 new events, indicates "a very sharp increase in recent months corresponding with the start of the pandemic H1N1 influenza....The average number of new events posted per month during the pandemic period of April to September 2009 was 68.0 versus 8.6 during the preceding five years, indicating an unprecedented increase in reporting during the pandemic period." At the same time, there was a corresponding sharp decrease in the reporting of other threats - to "a significantly low rate". For instance, in July 2009, the number of nonpandemic-related threads posted to EWRS dropped to zero.

"These results suggest an important impact on the notification process of events in case of a situation requiring extensive mobilisation of public health resources. It emphasises the importance keeping an appropriate balancing of resources during sustained emergencies, in particular in view of a possible second wave of pandemic influenza cases, to ensure prompt detection and reporting of potential concomitant emerging threats."