* UK − DEFRA: Department for Environment, Food and Rural Affairs.
** Limited by culture.

Limitations To The Minimum Log Reduction − For Viruses

The log reduction value obtainable for viruses depends on the actual starting titre achievable for that virus. In standard tests, such as EN 14476, the virus strains are selected to be grown up to high titres (i.e. poliovirus 1 can be grown to > 1 x 10⁹ TCID₅₀ units and Adenovirus 5 can be grown to >1 x 10¹¹ TCID₅₀ units).
However, many viruses cannot be grown to such high titres, thus not enabling a 4 Log reduction to be achieved. Assay sensitivity is also compromised by the requirement to neutralise residual disinfectant action by dilution of the virus/disinfectant suspension. Viral log reductions of 3 are set in some standards for this reason (e.g. this is acceptable to the US Environmental Protection Agency), and these are recorded as a minimum log reduction.

¹ Aspergillus niger

EN 1650 Pass rate is a Log 4 reduction for fungi.