Surveillance of acute flaccid paralysis (AFP) in Lombardy, Northern Italy, from 1997 to 2011 in the context of the national AFP surveillance system

An Acute Flaccid Paralysis (AFP) surveillance system was set up in Lombardy (Northern Italy) in 1997 in the framework of the national AFP surveillance system, as part of the polio eradication initiative by the World Health Organization (WHO). This surveillance system can now be used to detect Poliovirus (PV) reintroductions from endemic countries. This study aimed at describing the results of the AFP surveillance in Lombardy, from 1997 to 2011. Overall, 131 AFP cases in Lombardy were reported with a mean annual incidence rate of 0.7/100000 children < 15 years of age (range: 0.3/100000-1.1/100000). The sensitivity of the surveillance system was optimal from 2001-2003. The monthly distribution of AFP cases was typical with peaks in November, in January, and in March. The major clinical diagnoses associated with AFP were Guillain-Barre Syndrome (GBS, 40%) and encephalomyelitis/myelitis (13%). According to the virological results, no poliomyelitis cases were caused by wild PV infections, but two Vaccine-Associated Paralytic Paralysis (VAPP) cases were reported in 1997 when the Sabin oral polio vaccine (OPV) was still being administered in Italy. Since a surveillance system is deemed sensitive if at least one case of AFP per 100,000 children < 15 years of age is detected each year, our surveillance system needs some improvement and must be maintained until global poliovirus eradication will be declared.