A method and a system is provided for inactivation of Infectious Pancreatic Necrosis Virus (IPNV) comprising illuminating a liquid containing IPNV with a lamp emitting a continuous broad band of ultraviolet (UV) light. The UV lamp may be “tuned” to optimize IPNV inactivation. The lamp may be a medium pressure UV lamp that emits UV light having wavelength between 260-400 nm and preferably, between 260-300 nm. The pressure of the lamp may be greater than 1.6 bar, 3 bar and preferably is 7 bar. The lamp may be composed of PS (synthetic quartz).