The phrase "deadly pandemic" refers to a serious and widespread outbreak of a disease or illness that can cause a large number of people to become sick and even result in death. Full definition
They were particularly interested in the virus's molecular engineering because the 1918 «Spanish flu» was the most deadly pandemic in history, killing 20 million to 40 million worldwide. (discovermagazine.com)
It is considered the most deadly pandemic in modern history, infecting one third of the world's population. (bookbrowse.com)
Back to the Future If not anthrax or Ebola, which pathogens might spawn the next deadly pandemic in our midst? (discovermagazine.com)