  Metagenomic datasets from pangolin tissue specimens have previously yielded
SARS-related coronaviruses which show high homology in their receptor binding
domain to SARS-CoV-2, suggesting a potential zoonotic source for this feature
of the human virus, possibly via recombination (Liu et al. 2019, Lam et al.
2020, Xiao et al. 2020, Liu et al. 2020). Here we re-examine these published
datasets. We report that only a few pangolin samples were found to contain
coronavirus reads, and even then in low abundance, while other non-pangolin
hosted viruses were present in higher abundance. We also discovered extensive
contamination with human, rodent, and other mammalian gene sequences, which was
a surprising finding. Furthermore, we uncovered a number of pangolin CoV
sequences embedded in standard laboratory cloning vectors, which suggests the
pangolin specimens could have been contaminated with sequences derived from
synthetic biology experiments. Finally, we discover a third pangolin dataset
(He et al. 2022) with low levels of SARSr-CoV sequences and unambiguous
extensive contamination of several pangolin samples. For these reasons, we find
it unlikely that the pangolins in question had a coronavirus infection while
alive, and all current versions of the cited papers claiming a zoonotic
infection of pangolins with a SARS-r CoV require substantial corrections and
should be retracted until such corrections are made.
