Strep infections, rather than the flu virus itself, may have killed most people during the 1918 influenza pandemic. This suggests that some of the most dire predictions about a potential new pandemic could be exaggerated.
Scientists looked at the available information regarding the 1918 flu pandemic, which killed anywhere between 50 million and 100 million people globally in the space of about 18 months. Some research has shown that on average it took a week to 11 days for people to die, which fits in more with the known pattern of a bacterial infection than a viral infection.
People with influenza often get what is known as a "superinfection" with a bacterial agent. In 1918 it appears to have been Streptococcus pneumoniae.
Many projections for a new pandemic have been based on a worst-case 1918 scenario, in which tens of millions of people would die globally. However, since strep is much easier to treat than the flu using modern medicine, a new pandemic might be much less dire than it was in the early 20th century.