Coronavirus was circulating in Italy as early as September 2019, scientists there have claimed.
The World Health Organization says COVID-19 was unknown before the outbreak was first reported in Wuhan, in central China, in December. A few months later, the first official cases were detected in Europe.
However, scientists in Italy say they have found evidence the virus was circulating much sooner by checking blood samples of patients taking part in a cancer study.
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Samples from four patients, dating back to the start of October 2019, were found to contain antibodies, according to findings published by Milan's National Cancer Institute (NCI).
The results mean they would have caught coronavirus in September - some five months before Italy recorded its first official COVID-19 patient on 21 February, in a town near Milan, in the northern region of Lombardy.
The study - published by NCI's scientific magazine Tumori Journal - found that 11.6% of blood samples from 959 healthy volunteers, who were enrolled in a lung cancer screening trial between September 2019 and March 2020, had developed antibodies well before February.
