Efforts to study the early stages of the coronavirus pandemic have received help from a surprising source. A biologist in the United States has ‘excavated’ partial SARS-CoV-2 genome sequences from the beginnings of the pandemic’s probable epicentre in Wuhan, China, that were deposited — but later removed — from a US government database.

The partial genome sequences address an evolutionary conundrum about the early genetic diversity of the coronavirus SARS-CoV-2, although scientists emphasize that they do not shed light on its origins. Nor is it fully clear why researchers at Wuhan University asked for the sequences to be removed from the Sequence Read Archive (SRA), a repository for raw sequencing data maintained by the National Center for Biotechnology Information (NCBI), part of the US National Institutes of Health (NIH).

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Partial SARS-CoV-2 sequences from early outbreaks in Wuhan were removed from a US government database by the scientists who deposited them.