EXPERT REACTION: Was COVID-19 in Europe in March 2019?
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A recent pre-print study has claimed to have found traces of COVID-19 in Spain in March 2019, well before the first reported case in Europe. The yet to be peer-reviewed research tracked SARS-CoV-2, the virus behind COVID-19, in wastewater with UK researchers arguing the findings raise questions around COVID's origins. Below an Australian expert responds.
Organisation/s: Australian Science Media Centre, The University of New South Wales
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Waste water sampling is useful as a means of surveillance because SARS-CoV-2 is shed in faeces. During the height of the epidemic in Boston, for example, one study showed higher levels of virus in wastewater in Massachusetts than the clinical surveillance data suggested, so it may be a more sensitive way of ascertaining prevalence of infection in a population, given 80% of infections are mild and even asymptomatic.
Finding positive samples in December and January is one thing - we know the epidemic had already started in China by then, and it is likely travellers brought the infection to Europe and the US at that time, so that’s not too surprising.
However, finding the virus in a single sample in March 2019 in Spain (but not other months between March and December) is curious. Where did it come from? Was it a false positive test? Was it from a traveller who visited Spain, and why did it not cause an epidemic? If it really was circulating, was in exactly the same virus or a milder or less contagious variant?
We have just published a paper using open source data and our epidemic intelligence observatory, Epiwatch, and found a signal for COVID-19 in November 2019 in Hubei province, China. So the epidemic is likely to have started earlier than December 2019.
There are also reports of many athletes getting sick after the World Military Games in Wuhan in October 2019 - the US team, for example, flew in and out of Seattle, which was ground zero for the US epidemic.
We also know that only half the initial cluster of cases in Wuhan went to the seafood market, and the very first documented two cases did not go to the market. So the origin of the virus is still a mystery. However, several lines of evidence point to an origin of the virus prior to December 2019.
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