A study by Milan's National Cancer Institute has found the coronavirus appears to have been circulating in Italy since as early as September 2019, signaling that COVID-19 might have spread beyond China months much earlier than previously thought.
The World Health Organization has said the disease was unknown before the outbreak was first reported in Wuhan in December.
And, Italy's first COVID-19 patient was detected on February 21 in a town outside Milan.
But the cancer institute looked at past lung cancer screenings and found that about 12% of volunteers in a screening trial had developed coronavirus antibodies between September 2019 and March 2020, and well before February.
A further specific antibodies test was carried out by the University of Siena for the same research.
A co-author of the study told Reuters that it showed four cases dated back to the first week of October were also positive for antibodies neutralizing the virus, meaning they had got infected in September. He also said that it showed the virus could remain in a populaton with a low lethality rate, only to surge again later.
Italian researchers had previously told Reuters in March that they reported a higher than usual number of cases of severe pneumonia and flu in Lombardy in the last quarter of 2019 - another sign that the new coronavirus might have circulated earlier than previously thought.