The last widespread circulation of wild poliovirus in Israel was 25 years ago, resulting in a national outbreak with cases of permanent paralytic polio . The major difference between the 1988 outbreak in Israel and other outbreaks of wild poliovirus infection in recent years in other developed countries [19,20] that used an IPV-only routine vaccination schedule, is the early detection of silent virus circulation through an existing early warning system, involving national environmental surveillance. This early detection allowed for further investigation and planning of a national response well in time.
An apparent single event of long-distance WPV1 importation from Pakistan, where the SOAS genotype has circulated in 2012, to Egypt, possibly by an asymptomatic carrier or carriers, and the further importation to Israel – a journey of thousands of kilometres – has resulted in nearly nationwide WPV1 spread. This widespread WPV1 circulation might have been facilitated by the substantial non-OPV immunised cohort of children, who were born after the withdrawal of routine OPV doses from the national immunisation programme in 2005.
Notably, the highly probable chain of events that lead to the re-introduction of WPV1 into Israel in 2013 is not the first of its kind. Other possible long-distance point importations into decades-long polio-free countries were identified, in Finland and the Netherlands, following the paralytic polio outbreaks of 1986 and 1992, respectively [19-22]. This is in contrast to the endemic, Middle-Eastern origin of the 1988 outbreak due to WPV1 in Israel [1,3,4].
The detection of WPV1 in 2013 in Israel should therefore alert polio-free countries and global health organisations, which could confront a similar situation, given the increased mobility of people and populations, as long as wild poliovirus continues to be endemic in several parts of the world. Furthermore, our findings are also relevant to the global debate related to polio preventive measures such as routine national environmental surveillance and reinstitution of combined IPV and OPV routine immunisation schedule, even in polio-free countries with high IPV coverage .