US Porcine epidemic diarrhea virus (PEDV) was 99.5% to a ________ variant.

• A. American
• B. European
• C. Chinese
• D. African

Answer: (C)

Understanding how viral genomes are used to trace origins helps explain why the US PEDV strain is said to be 99.5% identical to a Chinese variant. Porcine epidemic diarrhea virus is an RNA coronavirus, and scientists compare its genome sequences to see how closely related different outbreaks are. When the US outbreak sequences match a Chinese variant so closely, with about 99.5% nucleotide identity, it points to China as the near source of the strain that reached the US, rather than Europe or Africa. The tiny differences that remain are expected from viral mutation as it spreads. Thus, the data best support origin from China, not from European, American, or African lineages.