Although people dutifully wore masks, these provided only a very limited protection against the influenza virus during the flu epidemic of 1918-1919.
Teachers hand out antibacterial gel to students as they arrive during the first week of school in Mexico City in late August. It was a preventive measure to combat the possibility of an outbreak of swine flu.
Policemen in Seattle wore masks in 1918 to protect themselves from a deadly outbreak of influenza.
Hiram Diaz, 8, left, and his 6-year-old sister Adely Diaz wear protective masks in April in Mexico City. The current flu pandemic began with an outbreak in Mexico.
In this 1918 photograph, influenza victims crowd into an emergency hospital at Camp Funston, a subdivision of Fort Riley in Kansas. The flu, which is believed to have originated in Kansas, killed at least 50 million people worldwide.