Surveillance of poliomyelitis in Italy: a country of huge immigration impact

Although in 2015 poliovirus (PV) transmission has been reported at the lowest levels ever recorded, the spread of virus from the endemic countries can be continue; the high levels of immigration flows across the Mediterranean Sea jeopardize Italy for PV reintroduction. The “WHO Strategic Plan of the Global Polio Eradication Initiative” indicates the nationwide surveillance of Acute Flaccid Paralysis (AFP) as the gold standard for detecting cases of poliomyelitis. In addition, systematic Environmental Surveillance (ES), seeking the presence of Poliovirus and Non-Polio-Enterovirus (NPEV) in sewage, is recognized as a powerful tool to confirm PV circulation in absence of AFP cases, especially in polio-free countries. The annual average incidence rates of AFP recorded in Lombardy (Northern-Italy) from 2012 to 2015 in patients<15years was 0.94/100’000 (range: 0.47/100’000-1.42/100’00) and in Italy was 0.78/100’000 (range: 0.73/100’000-0.83/100’00) [From:CISID-database, report 2012-2014]; the sensitivity of the AFP surveillance system is considered adequate whit an incident index ≥1.00/100’000. According to virological results, none AFP case was caused by PV infection. In the framework of the ES conducted in Milan, 264 wastewater samples were collected from 2012 to 2015 and none PV was isolated. In contrast, NPEV were detected in 65.2% (172/264) of tested samples. Keeping strong and encouraging both AFP surveillance and ES is crucial to ensure the PV will not return unnoticed in Italy and, finally, to achieve the global polio eradication goal.