The death rates in Philadelphia and St Louis during the 1918 Spanish flu pandemic demonstrate the importance of social distancing (Credit: National Academy of Sciences USA 2007)
Countries around the world are implementing measures to encourage social distancing (Credit: Getty Images)
In some places people are finding inventive ways to maintain their distance from others (Credit: Getty Images)
In Palembang, South Sumatra, seats on trains have been marked with red crosses to show people how to keep their distance (Credit: Getty Images)
The Italian town of Lodi put social distancing measures in place much earlier than Bergamo, where cases rose more sharply (Credit: Leverhulme Centre for Demographic Science)