Environmental surveillance of re-emerging poliovirus (PV) amid the international spread of wild-PV

Background. In May 2014, the World Health Organization (WHO) declared the international spread of wild poliovirus (PV) a Public Health Emergency of International Concern (PHEIC) due to PV reintroduction in three major epidemiologic zones do to the populations move: in central Asia (from Pakistan to Afghanistan), in the Middle East (from Syria to Iraq) and in central Africa (from Cameroon to Equatorial-Guinea). Although there aren’t Temporary Recommendations in polio-free States, an increase in surveillance for PV are encouraged to detect any virus importation. While Acute Flaccid Paralysis (AFP) surveillance remains the gold-standard, Environmental Surveillance (ES) is a powerfully tool to detect PV in the absence of clinical cases, as recently shown in Israel. This activity had been set-up in Milan, Northern-Italy, as well as in other six Italian city, since 2006. Methods. From January 2014 to march 2015, 84 wastewater sample were collected bimonthly at the intel of 3 wastewater treatment plants located in the city of Milan and serving a population between 100,000 and 300,000 inhabitants. ES was conducted according to WHO guidelines (WHO/V&B/03.03). As such, after the virus concentration by two-phase separation, PV and non-polio Enterovirus (NPEV) were isolated in RD and L20b cell lines for the detection of Enterovirus and PV, respectively. Result. ES achieved the WHO performance indicator in the study period. According to the virological results none PV was isolated during ES but an high rate of NPEV was detected (57/84; 67.8%) without seasonal trend. Conclusion. ES has a great impact in routine monitoring of PV circulation, especially in polio-free countries, as previously assessed. In Milan, none PV was detected in the study period, supported the Italian epidemiological data. An improvement in the ES should be able to cover an higher rate of Italian population and detect rapidly eventual PV reintroduction. Main message. Because ES is a powerfully tool to detect PV in the absence of polio cases, this activity needs to be both encourage and improve in Italy as a routinely approach in PV eradication program.