Researchers at the University of Barcelona have said they detected the novel coronavirus in a frozen Barcelona wastewater sample from March 12, 2019, Anadolu Agency reported.

The findings were published in medRxiv, a well-regarded server that quickly publishes preprints of medical research while they are undergoing peer review.

Barcelona researchers began by analysing weekly samples from April 13 until May 25 and also studied frozen archival samples from earlier in the year, according to the article. The analysis detected the new coronavirus, named SARS-CoV-2, in Barcelona sewage as early as January 15 — 41 days before the first official case was confirmed in Barcelona.

This triggered researchers to go back even further, and they tested frozen samples from January 2018 to December 2019.