Origin, Evolution, and Virulence of Porcine Deltacoronaviruses in the United States

Ma, Yuanmei; Zhang, Yu; Liang, Xueya; Lou, Fangfei; Oglesbee, Michael; Krakowka, Steven; Li, Jianrong

Origin and evolution of deltacoronaviruses. In general, CoVs have high mutation rates and can easily undergo recombination and deletion events that lead to altered tissue tropism, transmission routes, and host specificity. Birds are reservoirs for avian deltacoronaviruses (15) (16) (17) . These avian deltacoronaviruses may adapt and jump to some mammalian species. Interestingly, the first mammalian source of deltacoronavirus was detected in rectal swabs of Asian leopard cats at live-animal markets in Guangdong and Guangxi Provinces in China (23) . It was found that 2.4% of Asian leopard cats (35 out of 1,453 samples) were positive for deltacoronavirus. It was also found that 1.1% of Chinese ferretbadgers (11 out of 934 samples) were also positive for deltacoronavirus, which shares 100% homology with the Asian leopard cat CoV based on the RdRp domain and the S gene sequence (23) . Interestingly, the PdCVs of both Hong Kong strains and U.S. isolates share more homology with deltacoronaviruses of Asian leopard cats and Chinese ferret-badgers than avian deltacoronaviruses, suggesting that Asian leopard cats and Chinese ferretbadgers are intermediates for interspecies transmission of PdCV. At this time, we do not know if deltacoronaviruses are present in U.S. bird populations or other U.S. mammals (such as domestic cats). Clearly, a better understanding of the origin and evolution of the U.S. PdCV will await the detailed epidemiological study of deltacoronaviruses in the birds and mammals in the United States.