Lessons from a public health emergency--importation of wild poliovirus to Israel.

n engl j med 371;11 nejm.org september 11, 2014 981 trict tested positive for wild poliovirus type 1.1 Additional analyses retrospectively confirmed that the virus had already been present in February 2013 in samples from sewage-treatment plants near the capital of the South district. The virus found in these samples was closely related to polioviruses that have been circulating in polioendemic Pakistan since 2012 and to the poliovirus that had been isolated from sewage samples in neighboring Egypt in December 2012.2 This public health emergency posed two major challenges for decision makers in Israel. The first one concerned the sustainability and interpretation of our supplementary environmental surveillance. Since the last poliomyelitis outbreak in Israel in 1988,1 the country has developed the capacity in our environmental laboratories to detect pathogens such as polioviruses in very low quantities within large volumes of sewage, and we have fully deployed this high-sensitivity detection on a national scale. This system routinely covered approximately 30 to 40% of the population in a representative fashion,2 and it was substantially intensified beginning in June 2013, shortly after the detection of the wild poliovirus importation. The number of sewage sites being sampled increased from a range of 8 to 10 per month to 80 per month at the height of the effort, to keep up with poliovirus activity.2 The coverage of the sampling was thereby expanded to include as much as 80% of Israel’s population, and the sampling frequency was increased from monthly to weekly. This dramatically enhanced environmental surveillance, which has continued in 2014, has demonstrated the gradual clearance of the imported wild poliovirus since September 2013. Samples at all sampling sites outside the epicenter sites in southern Israel began testing negative quite rapidly, and later, the wild poliovirus gradually disappeared from the epicenter sites themselves — findings that indicated the fading out of human-to-human transmission of the virus and its excretion in feces. The latest surveillance data (from August 14, 2014) confirm the consistently negative results for all tested sites in Israel. Lessons from a Public Health Emergency — Importation of Wild Poliovirus to Israel