Since the COVID-19 pandemic began in Wuhan, China in December 2019, we have seen the virus spread to over 160 countries. Several countries have experienced large outbreaks, including China, South Korea, Italy, Iran, Spain and France, with the US and UK seeing rapidly increasing numbers. But most countries in the world have reported very few to no cases of COVID-19.
While it is likely that the virus has not yet reached and started localised transmission in every country, many of these countries have strong travel, migration or trade relationships with China. This raises the question: are these low case numbers due to the virus not reaching or establishing infections, is it due to effective border control, or does it reflect a lack of screening and reporting?
The spread of an infectious disease from its country of origin is a complicated process involving many factors, but at its core, it is related to the movement of people. There are several parameters that can be used to coarsely estimate movement: travel (inbound and outbound), migration, trade and proximity. Looking at the number of COVID-19 cases in the context of the ranked order of flow of people and goods between China other countries, we see the following (as of March 15):
While this is a vastly simplified analysis of population movement, it is striking that there are only 63 cases reported in all of Russia. Given that Russia has very strong travel, emigration, immigration and trade relationships with China, its very low case numbers raise questions, especially as other countries with comparably close relationships (Japan, South Korea and the US) are experiencing significant local transmission.