Testing thermal resistance of viruses.

Representative viral strains recommended for virucidal testing of biocides in human medicine were used for testing viral resistance to dry heat using the new Keredusy hot instrument. The results demonstrate that poliovirus type 1 could be inactivated by treatment at 75 degrees C for 1 h. For inactivation of adenovirus type 5, 2 h at 85 degrees C was needed. The infectivity of polyomavirus SV40 could only be influenced significantly by a temperature of 95 degrees C over a period of 1 h, whereas vaccinia virus and bovine viral diarrhea virus needed a time interval of 2 h at 95 degrees C. The infectivity of bovine parvovirus could not be influenced significantly by exposure to 95 degrees C for 2 h. In conclusion, human viruses and their surrogates for testing biocides may have a considerable thermal resistance that makes them difficult to be inactivated only by dry heat.