Last year, Israel's polio-free status was seriously challenged. On May 28, 2013, a sample obtained during routine supplementary environmental surveillance at a sewage-treatment plant in the South district tested positive for wild poliovirus type 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 polio-endemic Pakistan since 2012 and to the poliovirus that had been isolated from sewage samples in neighboring Egypt in December 2012.2