Italian scientists who analyzed blood samples of volunteers of a cancer trial found that some had antibodies to COVID-19 as early as September of last year. The researchers at the National Institute of Milan examined the blood of 1,000 asymptomatic people who took part in the trial between September 2019 and March 2020 in the city of Milan, which was the first area in Italy hit by the coronavirus.

Although the World Health Organization first announced that the disease was originally reported in Wuhan, China during the month of December, the latest findings reveal that it was active in Europe much earlier.

According to Newsweek, the researchers say their study may reshape the history of the pandemic.

“This study shows an unexpected very early circulation of SARS-CoV-2 among asymptomatic individuals in Italy several months before the first patients was identified,” wrote the study authors. “Finding SARS-CoV-2 antibodies in asymptomatic people before the COVID-19 outbreak in Italy may reshape the history of the pandemic.”

Although Italy’s first COVID-19 case was not confirmed until Feb. 21, the researchers discovered that over 11% of the people had specific antibodies to the virus long before that date, including 14% from blood samples analyzed in September 2019.

It is not the first time researchers have found evidence of early infections. According BBC News, a patient in France was treated for pneumonia on December 27 and the nasal swab taken at the time was later tested for COVID-19. It came back positive, indicating that the virus arrived in Europe much earlier than previously thought.

And some studies have suggested that even in China, the disease was rampant long before the official announcement last December.

Researchers at Harvard Medical School used satellite data and found that there was up to a 90% increase in hospital automobile traffic in China in the fall of 2019 compared to the previous year, and that at Wuhan Tongii Medical University, located in the city where the virus was believed to originate, the spike in car traffic was noted as early as mid-September.

Dr. John Brownstein, who led the study, said that the data showed “more cars in a hospital, the hospital’s busier, likely because something’s happening in the community, an infection is growing, and people have to see a doctor.”

Chinese officials did not notify the World Health Organization until December 31 that a new pathogen had been spreading in Wuhan, according to ABC News.