Poliovirus reintroduction monitoring through the acute flaccid paralysis and environmental surveillance: result of these activities in Lombardy, 2014

Introduction. Nowadays, Polio remains endemic in three countries – Afghanistan, Nigeria and Pakistan – and all countries remain at risk of importation of polio, especially in countries from west Africa to the Horn of Africa and where high levels of immigration are reported. The WHO Strategic Plan of the Global Polio Eradication Initiative indicates the Acute Flaccid Paralysis (AFP) surveillance and the Environmental Surveillance (ES) as a crucial activities in order to detect eventual poliovirus (PV) reintroduction in polio-free countries and to achieve PV worldwide eradication. Nowadays, AFP surveillance is the gold-standard but ES is able to detect PV reintroduction without clinical outcomes. This study aimed at describing the results of the AFP surveillance and ES in Lombardy, Northern-Italy, in 2014. Methods. The surveillance activities were carried out according to WHO guidelines (AFP surveillance: WHO/IVB/04.10; ES: WHO/V&B/03.03). All children < 15-years-old who fulfilled the WHO definition for AFP case and place in Lombardy region (Fig.1) were enrolled in this study and their stools were collected as soon as possible. Result During ES, wastewater sample was collected regularly twice a month at the intel of 3 wastewater treatment plants located in Milan. AFP stools and wastewater sample were investigated to detect PV and non-polio Enterovirus (NPEV) by virus isolation and PCR.Thirteen AFP cases were reported with a incidence rate of 1/100 000 children < 15 years of age (median age: 36 months) The sensitivity of the surveillance system was good (Table 1). The major clinical diagnoses associated with AFP were Guillain-Barré Syndrome (7/13; 53.8%). According to the virological results, none AFP case was caused by PV infections. NPEV was detected in one patient with conclusive diagnosis of Hand, Food and Month Disease (HFMD). During ES, 70 wastewater samples were collected and none PV was isolated; on contrary an high rate of NPEV was detected (49/70; 70%). Conclusion. Due to high levels of immigration across the Mediterranean sea, Italy remains at risk of PV reintroduction. In Italy, AFP surveillance has been set-up in 1997 at regional level while ES has been established since 2005-2006 in Milan and few other Italian cities. The results of these activities confirm the polio-free status. AFP surveillance and ES must be maintained until global PV eradication will be declared. Although AFP surveillance remains the gold-standard, ES is a powerful tool to detect PV in the absence of polio cases. Thus, ES in Lombardy, as well as in other Italian Region, needs to be improve.