https://academic.oup.com/cid/advance-article/doi/10.1093/cid...
Edit: removed incorrect conclusion
Without Chinese data the origin will remain a mystery.
https://www.reuters.com/article/us-health-coronavirus-spain-...
Kept searching for followups, didn’t see anything till this:
https://www.sciencedirect.com/science/article/pii/S004896972...
That’s from 21 January 2021 and says:
“So far unpublished data, analysing retained wastewater samples from Barcelona, Spain, taken in March 2019 showed positive RT-qPCR results for SARS-CoV-2 (Chavarria-Miró et al., 2020). The authors conclude that the virus was introduced to the Barcelona population due to global travel and remained undetected.”
So as of then, still unpublished.
The French study has just been published last week [0]. It is based on a vast cohort study in which serum samples were collected regularly. They tested older samples and found some anti-SARS-CoV-2 antibodies. The article also mentions an Italian study with similar results [1].
[0] https://link.springer.com/article/10.1007/s10654-020-00716-2
[1] https://journals.sagepub.com/doi/10.1177/0300891620974755