Several pathogens are known to affect the respiratory tract of pigs resulting in decreased health and welfare. Porcine parainfluenza virus 1 (PPIV1) and swine orthopneumovirus (SOV) have been identified as novel viruses in pigs. The pathogenicity of PPIV1 has been investigated experimentally by one research group, whereas SOV is yet to be studied. In this experimental trial, two groups of eight pigs were inoculated with a European isolate of PPIV1 or a pool of SOV RNA-positive clinical nasal swa