Why did the infection spread from China?

With SARS and MERS, and now COVID-19, infectious diseases have been running rampant since the turn of this century. However, if we look into the past, it could be said that infectious diseases have been a constant throughout human history. During the modern period , in particular, the expansion of global transportation networks resulted in the expanded movement of people and goods worldwide, which in turn led to the spread of infectious diseases. Japan and the Western nations, which faced a heightened threat of infectious diseases as a result of their colonial holdings, deepened their research into tropical medicine to promote measures against diseases like malaria, cholera and the plague. At the beginning of the twentieth century, the Spanish flu wrought havoc in the background of the First World War. The League of Nations placed an emphasis on the issue of hygiene, bringing international cooperation to the measures taken against infectious...