Infection Spread Summary is a data chart.
It displays healthy countries on the left, infected countries in the center, and destroyed countries on the right. If an infected country still has healthy people, it is indicated with a blue heart to the left of the name. It is not a graph, like the rest, but merely a list of the status of countries. With almost all disease types, when all the countries are listed as Destroyed, you've won the game. However, if even one country is still in the Healthy section when all your disease's victims have died, you have lost the game. This is a quick way to check which countries are yet to be infected, fully infected, and destroyed.
This will be handy at the end of the game when only a few countries are still uninfected. This will tell you who needs to be destroyed next. Additionally, any country that isn't completely infected will have a blue heart next to it.