David McCandless at Information is Beautiful has a great chart plotting diseases based on how infectious they are (as measured by the average basic reproduction number, or the average number of people one person with the disease will infect) and how deadly they are (as measured by the percentage of cases that end in death):
Note that, even if they don't kill a huge share of infected people, very contagious diseases can still produce a very high death toll. In 2012, only about 0.3 percent of people infected with malaria died, but because 207 million people were infected, that added up to 627,000 deaths, a still staggering total.
The chart also hammers home the importance of treatment and vaccination. Untreated, HIV has a fatality rate of about 80 percent, which falls to a couple percent with treatment. Meanwhile, two of the most infectious diseases — measles and whooping cough — have safe, effective vaccines available for them, but fewer people are getting them due to dangerous fearmongering by celebrities. If you want to know more about this unfortunate phenomenon, check out this video:
Thanks to Eileen Shim at Mic for the pointer on the chart.