Workers disinfecting buses in BrazilCoronaviruses have long been a threat to human health. At the milder end of the scale, several kinds are known to trigger common colds. At the other extreme, two coronaviruses have caused recent outbreaks of deadly illnesses: severe acute respiratory syndrome (Sars) and Middle East respiratory syndrome (Mers). But the impact of all these has been minor compared with that of Sars-CoV-2, the new coronavirus behind the Covid-19 pandemic we are currently living through. In December 2019, reports started to emerge that a coronavirus never before seen in humans had begun to spread among the population of Wuhan, China. In only a few months, the new coronavirus has reached nearly every world nation, infecting more than 2 million people and claiming more than 120,000 lives (both these official figures are believed to be far fewer than the actual numbers). Efforts to prevent the disease spreading have included lockdowns in many countries. So what have we learned so far, and how might that knowledge be used to bring about an end to this pandemic?
1. What are coronaviruses?
A computer generated image of Sars-CoV-2Coronaviruses are a family of viruses that affect mammals’ respiratory (breathing) systems. They are grouped into four kinds: alpha, beta, delta, and gamma. Most affect only animals, but a few, the alpha and beta types, can are also transmissible to humans. Before now, just two coronaviruses have caused epidemics. The first of these was Sars, which broke out in China in 2002. The second was Mers, or Middle East respiratory syndrome coronavirus, which emerged in Saudi Arabia in 2012.
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