Enterovirus circulation in wastewater and behavior of some serotypes during sewage treatment in Monastir, Tunisia.

Enteroviruses were monitored in three wastewater plants that used activated-sludge, trickling-filter, and oxidation-ponds processes, respectively, from October 2000 to September 2001 in the region of Monastir, a tourist zone situated in the center of the Tunisian coast. Isolation and serotyping were conducted as recommended by the World Health Organization. Enteroviruses were present during the whole period of investigation. From February to June, however, enterovirus titers decreased (cytopathic effect < 45 percent); they increased during summer and autumn and at the beginning of winter. Among the isolates in the 120 wastewater samples that were collected, eight were found to be poliovirus vaccine-related, 30 were echoviruses, and 8 were untypable. Echovirus Type 6 was the serotype most frequently isolated (in 49 percent of samples) during all seasons, Some serotypes appeared occasionally (echovirus types 11, 25, and 13). Isolation of serotypes varied according to the step of wastewater treatment. Poliovirus 1 and Echovirus 6 were the most resistant serotypes.