Use the map on world life expectancy to answer the following question:

A global map shows average life expectancies in 2010. The key shows a range from 40 years to 80 years. All of Sub Saharan Africa has a life expectancy of 60 years or less, as do Iran, Afghanistan, Pakistan, and some countries in Southeast Asia. North African and Middle Eastern life expectancies mostly fall between 70 to 75 years, while virtually all of South, East, and Southeast Asian, as well as Eastern Europe and Russia, have life expectancies of 65 to 75 years. This excludes Australia, Japan, and New Zealand, which have life expectancies of over 80 years. Most Western European countries also have life expectancies of 80 years. All North American countries except Greenland have a life expectancy of at least 75 years, while most of Central and South America has a life expectancy between 65 and 75 years.
Creative Commons Attribution-Share Alike 3.0 Unported

Which of the following is the most likely culprit for why Africa has such a low life expectancy rate compared to almost everywhere else?

The spread of the AIDS virus
The spread of SARS
The spread of Asian flu
The spread of H1N1