English: Animation of a simulated pandemic H1N1 2009-like pandemic. The simulation was initialized with 1,000 infected individuals in Mexico City on March 29 with . Red dots on the map indicate cities with infected individuals, with the size of the dot proportional to prevalence. Light blue arcs indicate that an infected person travels to a city with no infected individuals. On the right, infection prevalence is plotted for three regions: North (cities north of the Tropic of Cancer, in red), South (cities south of the Tropic of Capricorn, in blue), and tropics (cities between the two tropics, in green).