Covid-19 has made its presence felt around the world. Photo / AP

Big read: Coronavirus - How Covid-19 shook the world

In Wuhan, a riverside metropolis of some 11 million in Central China, something rare happened. From a crowded, poorly ventilated market in the heart of the city, where rubbish could be seen piled on wet floors and livestock were kept mere metres from other animals freshly slaughtered and skinned, came a new type of virus. Two years before, Smithsonian Magazine published an investigation that warned how these stalls - and Chinese officials' hands-off approach to the obvious public health threat they posed - made perfect breeding grounds for the next big contagion. It finished with a portentous quote. "Viruses don't need visas or passports. They just travel."

In a few short months, the coronavirus Covid-19 has changed our lives and brought the world to a virtual standstill. Herald science reporter Jamie Morton traces how it happened.