Removal of astrovirus from water and sewage treatment plants, evaluated by a competitive reverse transcription-PCR

Quantification of human astrovirus genogroups A and B was undertaken with sewage and water samples, collected from the Greater Cairo area in Egypt from November 1998 to October 1999, by a competitive reverse transcription (RT)-PCR with an internal control. The number of RNA copies of genogroup A/liter in quantifiable samples ranged from 3.4 x 10(3) to 5.6 x 10(6) in raw sewage and from 3.4 x 10(3) to 1.1 x 10(4) in treated effluents, while the number of infectious units per liter in these samples as determined by cell culture RT-PCR (CC-RT-PCR U/liter) ranged from 3.3 x 10(1) to 3.3 x 10(3) in raw sewage and was 3.3 x 10(0) in treated effluents. On the other hand, the number of RNA copies/liter in quantifiable genogroup B samples ranged from 1.1 x 10(4) to 8.7 x 10(6) in raw sewage and from 1.1 x 10(3) to 6.2 x 10(5) in treated effluents, while the number of infectious units ranged from 3.3 x 10(1) to 3.3 x 10(5) CC-RT-PCR U/liter in raw sewage and from 3.3 x 10(1) to 3.3 x 10(2) CC-RT-PCR U/liter in treated effluents. These higher numbers of both RNA copies/liter and infectious particles of genogroup B may indicate the emergence of genogroup B in the area. Additionally, genogroup B astrovirus exhibited a higher resistance to removal treatments with regard to the number of RNA copies per ml. When the equipment for real-time approaches is unavailable, a competitive PCR or RT-PCR with an internal control may be employed for virus quantification in validations of the efficiency of virus removal treatments.