Today, on the continent of Africa, nearly 30 million people have the AIDS virus, including 3 million children under the age of 15.

CNN: Transcript of State of the Union

Last year, however, Simonsen and Viggo Andreasen concluded that the true R-naught of the 1918 flu virus was probably somewhere between 3 and 4.

CNN: Scientists dig for lessons from past pandemics

Comparing the two rates of infection, patients taking antiretroviral drugs were 96.3% less likely to pass on the virus.

WSJ: AIDS Study Marks Prevention Breakthrough With Antiretroviral Drugs

In 2011, Foldit players needed only 10 days to produce an accurate 3-D model of the Mason-Pfizer monkey virus, a protease whose structure had stumped scientists for 15 years.

CNN: People and computers need each other

West Nile virus peaked in 2002 and 2003, when severe cases of the disease reached nearly 3, 000.

BBC: West Nile virus death toll in US jumps by a third