Coronavirus: what have scientists learned about Covid-19 so far?

Medical researchers have been studying everything we know about Covid-19. What have they learned - and is it enough to halt the pandemic?

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Coronaviruses have been causing problems for humanity for a long time. Several versions are known to trigger common colds and more recently two types have set off outbreaks of deadly illnesses: severe acute respiratory syndrome (Sars) and Middle East respiratory syndrome (Mers).

But their impact has been mild compared with the global havoc unleashed by the coronavirus that is causing the Covid-19 pandemic. In only a few months it has triggered lockdowns in dozens of nations, and the disease continues to spread.