Coronavirus may have lain dormant across the world and emerged when environmental conditions were right for it to thrive - rather than starting in China, an Oxford University expert believes.
Dr Tom Jefferson, senior associate tutor at the Centre for Evidence-Based Medicine at Oxford and visiting professor at Newcastle University, says there is growing evidence the virus was elsewhere before it emerged in Asia.
Last week, Spanish virologists announced they had found traces of Covid-19 in samples of waste water collected in March 2019, nine months before the disease was seen in China.
Italian scientists have also found evidence of the virus in sewage samples in Milan and Turin from mid-December, many weeks before the first case was detected, while experts have found traces in Brazil from November.
Dr Jefferson believes many viruses lie dormant throughout the globe and emerge when conditions are favourable. It also means they can vanish as quickly as they arrive.
"Where did SARS-1 go? It's just disappeared," he said. "So we have to think about these things. We need to start researching the ecology of the virus, understanding how it originates and mutates. We may be seeing a dormant virus that has been activated by environmental conditions. There was a case in the Falkland Islands in early February. Where did that come from?
"There was a cruise ship that went from South Georgia to Buenos Aires and the passengers were screened and then on day eight they got the first case. Was it in prepared food, defrosted and activated?
"Strange things like this happened with Spanish flu. In 1918, around 30pc of the population of Western Samoa died of Spanish flu and they hadn't had any communication with the outside world.
"The explanation could only be that these agents don't come or go anywhere. They are always here and something ignites them."
Dr Jefferson believes that the virus may be transmitted through the sewerage system or shared lavatory facilities, not just through droplets expelled by talking, coughing and sneezing. (© Daily Telegraph, London)