Aims:  The objective of this study was to estimate UV254 inactivation constants for four viral pathogens: influenza virus type A, porcine respiratory and reproductive syndrome virus (PRRSV), bovine viral diarrhoea virus (BVDV) and reovirus.

Methods and Results:  Viruses in culture medium were exposed to one of nine doses of UV254 and then titrated for infectious virus. Analysis showed that viral inactivation by UV254 was more accurately described by a two-stage inactivation model vs a standard one-stage inactivation model.

Conclusions:  The results provided evidence for the existence of two heterogeneous viral subpopulations among the viruses tested, one highly susceptible to UV254 inactivation and the other more resistant. Importantly, inactivation constants based on the one-stage inactivation model would have underestimated the UV254 dose required for the inactivation of these viruses under the conditions of the experiment.

Significance and Impact of the Study:  To improve the accuracy of estimates, it is recommended that research involving the inactivation of micro-organisms evaluates inactivation kinetics using both one-stage and two-stage models. These results will be of interest to persons responsible for microbial agents under laboratory or field conditions.