[A two-stage technique for concentration of viruses from solutions with low virus titers (e.g., drinking water)].

The evidence of viruses in drinking water is an important component of studies of viruscirculation between man and his environment. In the two-stage concentration technique presented in this paper the method of aluminium sulphat flocculation, verified in more than 1300 investigations, is the first stage. In the second stage, aluminium hydroxide gel is at first dissolved with 1 ml of citric acid sodium citrate buffer at pH 4,7. The physico-chemical aspects of the lysis are discussed. It is from the lysate, that is not toxic for viruses, that viruses are separated by ultracentrifugation and inoculated on cell cultures. Owing to considerable constriction effect of about 20 000:1 is the method especially suitable for evidence of viruses in solutions with low virus titers (e.g. drinking water) as confirmed by a series of tests.