What kinds of people caught Spanish influenza most easily and what kinds died in greatest percentages? If we could answer these two questions, then we would have some hints as to what to do if the disease or something like it returned.

Spanish influenza was not a typical communicable disease in its choice of people to infect and kill. Unlike tuberculosis, typhoid fever, and venereal disease, it did not show a clear preference for the poor, the ill-fed, ill-housed, and shabbily clothed. Sometimes there was a discernable correlation between flu, pneumonic complications, and crowded living conditions—breath-borne viruses are obviously more easily transmitted in cramped quarters, and the quarters of the poor are more often cramped than those of the rich—but by and large the rich died as readily as the poor.

There were correlations between pregnancy and death by flu, and between working as a coal miner and death by flu. But these correlations don't lead us very far. A pregnant woman has one set of lungs to handle the affairs of two bodies, and a coal miner often has something less than a fully efficient set of lungs to handle the affairs of one often overworked body. It is to be fully expected that a greater proportion of pregnant women and coal miners would die of Spanish influenza, heart disease, or anything else that might put an extra strain on the human body.

Immigrants had a higher death rate from flu and pneumonia during the pandemic than people born in the United States. Immigrants born in Canada, Austria-Hungary, Poland, and Russia had higher death rates than those born in England, Ireland, and Germany.