The virus that causes the Covid-19 disease has now infected more than 54 million people across the planet, but the question of just where it came from remains a mystery. Researchers may have found a new link in this puzzle after discovering evidence suggesting the pathogen had infected people across Italy as early as September last year, or months before it was first identified in the Chinese city of Wuhan. The unexpected finding “may reshape the history of [the] pandemic”, said the team led by Dr Gabriella Sozzi, a life scientist with the National Cancer Institute of Milan, in a peer-reviewed paper published last week in the Tumori Journal . The researchers tested blood samples from lung cancer screening tests in Italy and said they found antibodies specific to Sars-CoV-2, the virus causing Covid-19, in samples from patients all over the country in every month of a six-month trial that started in September 2019. The presence of the antibodies indicates the virus was infecting people in Italy before it was detected in Wuhan in late December. Tracing the pandemic to its origin could help prevent future outbreaks, and to this end the World Health Organization has in recent weeks separately pulled together an international team of scientists to investigate. However the puzzle of Covid-19’s origin has been further complicated by politics. As the virus spread and turned into a pandemic, both Beijing and the WHO were criticised over their initial handling of the outbreak. WHO-backed probes move forward to try to shed light on early days of coronavirus US President Donald Trump attacked the WHO, saying it was compromised by China interests, while others in his administration alleged the virus came from a Chinese lab, though no evidence has been presented and many of the world’s leading virologists have rejected that theory. These allegations undermined international scientific collaboration and Beijing’s move to rein in its scientists from freely discussing the outbreak with the international media added to suspicions. China’s authorities also said any Covid-19 research by the nation’s scientists needed official government approval before it was submitted to international journals. However, as the political debate soured and occupied the headlines, medical research to try and track where and how the virus emerged continued. The US National Institutes of Health director Francis Collins said the virus could have been spreading quietly in humans for a long time based on its current adaptation to human cells. A study by Oxford University scientists on the virus’ mutation history suggested it likely emerged somewhere outside Wuhan. Institut Pasteur researchers in France found the viral strains circulating in their country were quite different from those in China. In Spain, Italy and Brazil, researchers identified the virus’ genes in sewage samples dated months before the disease was named as a pandemic. These studies were also made possible because Chinese scientists released the virus’ full genome sequence to researchers in other countries before getting approval from the government. But these findings, mostly based on computer modelling or isolated evidence, were not strong enough to overthrow the Wuhan-origin theory. Sozzi’s team examined the blood samples of nearly 1,000 participants in Italy’s nationwide cancer-screening programme last year. Blood does not contain the virus, which cannot infect or replicate in blood cells, but it carries antibodies. The human body’s immune system generates antibodies after an infection, and they are tailor-made to deal with different invaders. Commercial tests for the antibodies to Sars-CoV-2 have been criticised for inaccuracy, or so-called false-positive or false-negative results. This gained attention on Friday when billionaire Elon Musk, the chief executive of Tesla and SpaceX, said he received two negative and two positive results. To address this concern, Sozzi said the team used a specialised test with an accuracy exceeding 96 per cent. She said this resulted in more than 100 samples, or over 10 per cent of the participants, testing positive. The researchers said they were surprised by the prevalence of infections from the novel coronavirus, saying that from the first week of September to the end of February, there was at least one positive case from each of Italy’s 13 regions. Italy’s earliest coronavirus strains did not arrive from China, study suggests The pre-pandemic infection rates changed over time and regions, but the patterns were similar to what happened in the later disease outbreak. For instance, more than half of the cases were recorded in Lombardy, Italy’s worst-hit region when the disease emerged. According to the research paper, Sozzi’s team was still concerned the antibodies they detected were generated by an infection by another type of coronavirus. To eliminate this risk, they performed another test to see if the antibodies could neutralise Sars-CoV-2, which they did. To the question why Italian health authorities or doctors had not detected the virus earlier, the researchers said participants in the cancer screening did not show symptoms, which indicated a high proportion of asymptomatic carriers. From November, some doctors in Italy did report an unusual increase of severe respiratory ailments among the elderly and vulnerable populations, but these cases were labelled as flu. A government epidemiologist in Shanghai said China’s government would welcome the study and the significance of these findings went beyond politics. “Every human being wants to know where it came from,” he said, speaking on condition of anonymity as he was not authorised to talk to the media. Still, the research in Italy does again raise more questions. For instance, given the unusually high prevalence and possibly low mortality rate, could the virus circulating earlier in the country be different from those detected later? Other researchers have said that Africa, a continent with large areas lacking adequate health care, has also recorded far fewer deaths than originally expected. ‘Strange pneumonia’ seen in Lombardy in November, leading Italian doctor says Some scientists suspect that a previous prevalence of other types of coronavirus might have given an immunity boost to people in local communities. But what these viruses were and if they were linked to the origin of the Sars-CoV-2 virus still remains a puzzle. Medical research shows that many viruses did not originate in the place where they were first detected. HIV was first identified in the US in 1981, but the earliest known infection was later traced back to the Congo decades earlier. The Zika virus was first reported in some Pacific island countries, but is believed to have originated in Uganda. And the 1918 flu pandemic, which was first reported by the Spanish government and labelled the Spanish flu, had its earliest recorded outbreak in a military base in the US state of Kansas.