Swine acute diarrhea syndrome coronavirus (SADS-CoV), also known as porcine enteric alphacoronavirus (PEAV) or swine enteric alphacoronavirus (SeACoV), discovered in 2017 in China, is the fifth porcine coronavirus (CoV) identified in diarrheal piglets. SADS-CoV is a single-stranded, positive-sense RNA virus that belongs to the Deltacoronavirus genus of the Coronaviridae family within the Nidovirales order. The genome of SADS-CoV is approximately 27.2 kb in size and encodes two open reading frames (ORFs, ORF1a and ORF1b) and five structural proteins—spike (S), envelope (E), membrane (M), nucleocapsid (N), and an accessory protein ORF3—as well as NS7a/7b (putative accessory genes). Clinical symptoms of SADS-CoV infection in piglets include acute diarrhea, vomiting, severe dehydration in piglets less than 5 days of age, and weight loss and death. The mortality rate of piglets less than 5 days old infected with SADS-CoV can be as high as 90%. The first outbreak of SADS-CoV-associated severe diarrhea occurred in Guangdong province, China, in February 2017. As of now, SADS-CoV had been detected in five provinces in China and had not been reported in other countries. SADS-CoV had a wide range of cellular fitness in vitro, including various rodent and human cell lines, suggesting that the virus has a potential threat of cross-species transmission to humans. While vaccines are not available for prevention, there are no effective treatments once the newborn piglets are infected with SADS-CoV. Therefore, controlling SADS-CoV relies heavily on biosecurity.