M. , Gibson, K. SECD can be eradicated and that most herds have been successful at long\term elimination of SECD after exposure (80%). However, unique properties of SECD, such as ineffective immunity through parenteral vaccination and a low oral infectious dose, play a major role in management of SECD. This review serves to describe the current knowledge of SECD and the characteristics of these viruses which provide both opportunities and challenges for long\term disease control and potential eradication from the US swine population. and genus with a 28?kb genome (Kocherhans, Bridgen, Ackermann, & Tobler, 2001). The virus was first described in Europe almost 40?years ago (Pensaert & de Bouck, 1978; Wood, 1977) and had been primarily maintained as an endemic pathogen in European and Asian swine populations until its introduction into North American in 2013. Since the 1990s, significant outbreaks of PED have Carbasalate Calcium occurred in The Czech Republic, Belgium, Hungary, Korea, Carbasalate Calcium China, Italy and Thailand (Song & Park, 2012) with a re\emergence of PED as a major swine disease in China around 2010 (Sun et?al., 2012; Wang et?al., 2013). Sequence analysis of US strains showed greater than 99% nucleotide identity to strains circulating in China between 2011 and 2012, indicating a probable Chinese origin of the US strain (Chen et?al., 2014; Huang et?al., 2013). Since 2013, PED has been a significant disease in the US swine industry, with 39 states and 3,750 premises being confirmed as positive for the virus as of December 2017 (USDA, 2017). In January 2014, porcine deltacoronavirus (PDCoV) emerged as another new swine enteric disease in US swine (Marthaler, Jiang, Collins, & Rossow, 2014; Wang, Byrum, & Zhang, 2014a). The virus is an enveloped, positive\sense RNA virus in the family and genus with a 25.4?kb genome (Wang et?al., 2014a). Prior to its US introduction, PDCoV had previously only been described in China in 2012 (Woo et?al., 2012). Sequence analysis of US strains showed approximately 99% nucleotide identity to the PDCoV strains previously detected in Hong Kong in 2012 (Wang, Byrum, & Zhang, 2014b). Since its introduction in 2014, PDCoV has spread throughout most swine\producing states, albeit at a lower prevalence rate than PEDV, with 21 states and 540 premises being confirmed as positive for the virus as of December 2017 (USDA, 2017). Subsequent to US introduction, PDCoV has since been detected in Thailand and Korea (Janetanakit et?al., 2016; Lee & Lee, 2014). Clinical disease and lesions caused by these two viruses are clinically indistinguishable from transmissible gastroenteritis virus (TGEV), a closely CDC18L related virus in the family and genus associated with diarrhoea in young pigs. However, all three viruses are antigenically distinct and cross\protection does not occur between PEDV, PDCoV and TGEV (Hofmann & Wyler, 1989; Jung, Hu, & Saif, 2016; Ma et?al., 2015; Pensaert & de Bouck, 1978; Pensaert, Debouck, & Reynolds, 1981; Zhang, 2016). Carbasalate Calcium Since PEDV and PDCoV emerged into the US swine population, much research has been performed to understand Carbasalate Calcium the factors around pathogenesis, immunity, introduction, transmission and management of these diseases; however, SECD continue to be introduced into new herds each week and gaps in knowledge remain. Tissue tropism, diagnosis, viral structure and proteins, physiochemical properties and pathophysiology of PEDV and PDCoV have been reviewed elsewhere (Jung & Saif, 2015; Jung et?al., 2016; Lee, 2015; Zhang, 2016). The current review describes the characteristics of these viruses, such as a low oral infectious dose, survival in feed and prolonged viral shedding, which create both opportunities and difficulties for future management and potential eradication. 2.?THE US EXPERIENCE The 1st case of PEDV confirmed by a veterinary diagnostic laboratory was in Ohio during the week of 15 April 2013 (AASV, 2013). Soon thereafter, PEDV spread rapidly and within weeks had been recognized in most swine\generating states in the United States (Number?1). By 3 June 2013, a mere 8?weeks after the initial case, PEDV was present in 12 claims and Iowa had 85 total positive.