Third Strain of Porcine Epidemic Diarrhea Virus, United States

To the Editor: In April 2013, porcine epidemic diarrhea virus (PEDV) was first reported (1).Since PEDV was detected, the virus has continued to spread throughout the United States and has now been reported in Mexico and Canada (2).PEDV was first reported in Europe in the 1970s and was later reported in Asia during the 1980s (3,4).PEDV outbreaks in Asia were more acute and severe than the PEDV outbreaks in Europe (4).In 2010, an increase, up to 100%, in illness and deaths in piglets was reported in China associated with PEDV infection (4-6).The original North American PEDV strains identified in 2013 caused severe illness and deaths in piglets and had a 99.5% nucleotide identity with Chinese strain AH2012 (1,7,8).Recently, a North American PEDV variant-INDEL strain was identified, which has been previously described ( 9).This spike gene deletion has been described in global PEDV strains, which may correlate with a less severe clinical presentation of PEDV.Although the PEDV variant-INDEL strain (OH851) was first reported in February 2014 by the Ohio Department of Agriculture, the PEDV variant-INDEL strains were first detected in June 2013, which suggests that the original PEDV strain mutated or that 2 different PEDV strains were introduced concurrently into the United States (2).The University of Minnesota Veterinary Diagnostic Laboratory has tested clinical samples from thousands of case-patients to determine the presence of PEDV by real-time reverse transcription PCR.Some of the PEDV-positive samples from case-patients were selected for PEDV spike gene sequencing per veterinarian's request, whereas other samples