How Covid-19 Went Global

The New York Times has created an informative story map which explains how coronavirus has quickly spread around the world. In How the Virus Got Out the NYT uses an interactive map to show how Covid-19 spread from just one city in China to the rest of the world.

The first known cluster of Covid-19 emerged around the Huanan seafood market in the city of Wuhan, China. Wuhan is a major transportation hub. By the time the Chinese realized that they were dealing with a new deadly virus and alerted the World Health Authority the virus had already spread to thousands of people. Covid-19 also emerged around the time of the Chinese New Year when millions of people travel to visit and stay with their families. Partly because of this movement over the New Year about 7 million people left Wuhan before travel restrictions were finally put in place.

During January international air travel continued as normal. This helped to spread the disease around the world. For example in an average month around 900 people fly from Wuhan to New York and over 2,200 to Sydney. Before international flights were stopped over 15,000 people flew from Wuhan to Bangkok. Researchers believe that around 85% of infected travelers flew undetected. In January the first case outside of China was reported in Bangkok.

By the time that China stopped international air travel Covid-19 had already spread to at least 26 countries. By March Covid-19 was detected across the globe and China was no longer the main driver of the outbreak. In fact during March the severe measures to halt the virus has slowed its spread in China, Singapore, Hong Kong and South Korea. However by this time Covid-19 was already spreading dramatically in Europe, the USA and many other countries around the world, where it still continues to spread.



It is also possible to visualize the spread of Covid-19 by mapping the number of confirmed cases around the world over time. In fact animated maps showing the spread of an epidemic can help us to learn more about how a virus is transmitted and how it spreads. For example HealthMap's Novel Coronavirus Covid-19 interactive map shows how Covid-19 quickly spread from Wuhan to the rest of China, through Asia and out to the rest of the world.

The map visualizes the number of reported Covid-19 cases in locations around the world by date. If you press the 'Animate Spread' button at the top-left of the map you can watch a day-by-day animation of the data showing how the disease spread around the globe in just a few weeks.

NBC New York's Covid-19 map actually works better as a visualization of how Covid-19 spread across the world. This map uses Johns Hopkins data to visualize the spread of Covid-19 over time. The NBC map includes a timeline control which allows you to more easily explore the data by specific date.