(2016a,b) infected conventional farrowed, 5-day-old non-suckling (fed with milk replacer and yogurt) piglets with a TC US S INDEL PEDV strain (IL20697/2014) and three other US highly virulent PEDV strains (IN19338/2013 , NC35140/2013 , and NC49469/2013 . The S INDEL PEDV strain (IL20697/2014) caused no or minimal clinical signs, lower reductions in body weight gain, more limited gross and microscopic lesions and lower fecal viral shedding and tissue PEDV antigen scores (Chen et al., 2016a) . However, individual and litter variations, as commonly observed in the field , were reported only in our piglet studies: the mortality of S INDEL Iowa106-inoculated piglets was 0% in three litters, but 75% in the fourth litter (Lin et al., 2015a) . In addition, the sows contact-exposed to their infected piglets became infected by S INDEL Iowa106 and two of four sows showed anorexia and diarrhea.