Figure 3: Enterovirus isolations from the Ayalon surveillance site (1A3) between 2007-2009 by month Sewage was collected at hourly intervals over 23-hour periods by an automatic composite sewage sampler that was lowered into the sewage system at the mouth of the Ayalon line just upstream of the Reading pumping station (see Figure 2). The catchment area of this site includes 350,000 individuals. The samples (1 L) were processed as reported [2]. A 2.5 ml aliquot of each concen- trated sewage sample was plated on BGM cell monolayers under plaque form- ing conditions. The number of plaques from each sample is graphed according to the month that the sample was taken. The three black arrows indicate sam- ples that also contained VDPV2 isolates belonging to epidemiological group 1..