Syndrome surveillance and molecular epidemiology for early detection and tracing of an outbreak of measles in Liguria, Italy

The performances of surveillance systems for measles in Europe are poorly investigated, despite the fundamental role they should play in the early detection of outbreaks and in the assessment of the progress towards elimination. A new chief complaint syndrome surveillance system has been developed in Genoa, Italy, using data from the Emergency Department records of the regional reference university hospital and its ability to early detect an outbreak of measles that began during the winter months of 2007/2008 was evaluated. For the 23-month period from January 2007 to November 2008, the Emergency Department registration and triage software was used to obtain the time series of daily counts, that were related with cases notified by the statutory notification system and detection and characterization data from the measles regional reference laboratory. One hundred fifty five cases of measles-like illness were identified by the syndrome surveillance system. Two epidemic threshold breakthroughs were able to anticipate the first notified case by 54 and 11 days. Globally, the new syndrome surveillance system allows the activation of the alert state with a specificity of 94.3% and a sensitivity of 91%. Molecular investigation showed the spread of the virus from United Kingdom to Piemonte and then to Liguria and allowed us to exclude the re- circulation of strains circulating in Northern Italy during the previous seasons. Syndrome surveillance integrated with a rapid detection and characterization of the agent responsible for the disease could be an effective, specific and sensitive tool for measles surveillance.