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{{ANENavegacionCapitulo (monografía COVID-19)|estructura temática=Estructura temática|seccion=[[Global context of the COVID-19 pandemic|Global context of the COVID-19 pandemic]]|capitulo=Origin and global diffusion of the pandemic}}
SARS-CoV-2 virus, known as COVID-19, was declared a health emergency towards the end of 2019 following an outbreak in the Chinese city of Wuhan. However, the results of water analyses gathered later from various parts of the world suggest it was already spreading before then. It presented initially as an acute health problem that spread from the original outbreak in Wuhan to other major metropolitan regions in China, particularly Shanghai, Chongqing and the Pearl River Delta (Guangzhou, Hong Kong, Shenzhen, etc.). Analyses of this expansion from data on public transport use, particularly high-speed trains –despite the small amount of data available from China–, explain the pandemic’s rapid spread throughout its vast territory. During the final months of 2019, it appeared the spread of the infection would be limited to China and to a few of its neighbouring Asian countries. However, international airports eased its spread to the rest of the world, and the World Health Organisation (WHO) declared it a global pandemic in early March 2020. The spread of the pandemic may be observed on the map on the ''[[:File:origins and spread of COVID-19|Origins and spread of COVID-19]]'', which shows the number of cases per country and month from February to July 2020. The peak of infections was registered in early April 2020. The lack of effective treatments for severe cases and little knowledge of how COVID-19 was transmitted during that period meant that it proved to be a highly lethal disease that resulted in tens of thousands of deaths. However, the severe lockdowns applied in many countries succeeded in gradually reducing the amount of deaths from that first wave.
The spatial diffusion of the pandemic across continents followed a predictable pattern. Initially, the virus spread from China to the rest of Asia. However, the strict lockdown measures adopted by some countries curbed the increase in infections there. Subsequently, the virus reached Europe, where it spread rapidly and soon reached the maximum number of infections in absolute terms. Later, COVID-19 was spread to the Americas, where it quickly spread. In fact, the Americas were the hardest hit continents, only lagging behind Europe for a few weeks. Finally, the pandemic also extended to the other continents yet with a much lower incidence, as happened in Africa, for example. There is, however, a possibility that the apparent lower prevalence in Africa may owe more to a lack of effective recording and to the fact that this new virus was just one more health problem in societies that are already highly vulnerable to all kinds of infectious and contagious diseases.
