To the Editor: Beginning in October 2010, porcine epidemic diarrhea (PED), caused by a coronaviral infection affecting pigs, emerged in China in an outbreak characterized by high mortality rates among suckling piglets. The outbreak overwhelmed >10 provinces in southern China, and >1,000,000 piglets died. This outbreak was distinguished by ≈100% illness among piglets after birth (predominantly within 7 days and sometimes within only a few hours) and death rates of 80%-100% (online Technical Appendix Table 1 , wwwnc. cdc.gov/EID/pdfs/11-1259-Techapp. pdf). Few sows or boars showed any clinical signs during the outbreak, which is not consistent with a recent report from Thailand (1). In that outbreak during late 2007, pigs of all ages were affected, exhibiting different degrees of diarrhea and no appetite. We characterized the genetic variation of the PED virus (PEDV) that caused a large-scale outbreak in China during 2010-2011 and compared it with viruses in other outbreaks. We also report a possible novel transmission pathway for PEDV.