The fact that a significant percentage of immigrants were Roman Catholic and, to a growing extent, Jewish, as well as poor and suffering from diseases, fed the fears and prejudices of nativist and other anti-immigrant groups. During the last decades of the nineteenth and first decades of the twentieth centuries, groups such as the Immigration Restriction League harnessed the ideas of new medical pseudosciences in their attempts to limit the diversity of immigrants. They blamed the perceived prevalence of certain diseases among eastern and central European immigrants, especially typhus and tuberculosis (TB), on natural genetic dispositions.
Tuberculosis was once widely considered to be a genteel or sensitive person’s disease. However, as it spread among the working classes in large U.S. cities, it became associated with poverty, squalor, and ethnic minorities, and sufferers were rounded up for isolation. A major outbreak in 1892 in New York City led to passage of the National Quarantine Act of 1893. San Francisco’s bubonic plague outbreak in 1900-1901 was very likely sparked by stowaways aboard a visiting Japanese freighter. However, its first known fatality was a Chinese immigrant who lived in a very poor Chinese neighborhood. Residents of Chinatown, fearing both mobs and the government, hid subsequent cases of plague until the outbreak could no longer be concealed. Anti- Chinese sentiment then flashed across the city, and there were calls to eradicate the Asian American neighborhood. Cooler heads prevailed, however, and modern antiplague measures kept the number of fatalities to only 122.
The popular linkage of disease and immigrants remained a major factor in U.S. public policy. Along the U.S.-Mexican border, perfunctory visual inspections for obvious signs of diseases were replaced by mandatory flea-dip baths for large numbers of very poor laborers and immigrants who sought work or refuge from the dislocations of the Mexican Revolution after 1917. The worldwide influenza pandemic that followed World War I may have killed more than 40 million people, including 675,000 Americans—a fatality rate that was five times the annual average for that disease. Like the war itself, the pandemic underlined the metaphorical shrinkage of the world and the increasing immediacy of threats that included disease. This sentiment resulted in the federal immigration restriction acts of 1921 and 1924.