Smallpox returns

A thing that would be best left forgotten sudenly returns... and kills one hundred million humans worldwide.

The last of the great pandemics of the Days of Fire. Smallpox returned, a disaster that nobody expected and nobody could prepare for. The initial outbreak happened in the Eastern United States, however before it was properly established as smallpox outbreak, it went worldwide due to one of the infected spreading the disease through the Hartsfield-Jackson International Airport in Atlanta/Georgia. By the time it was suppressed, it managed to kill 100 000 000 people worldwide.