Almost all Americans are immigrants or descended from immigrants, and yet the United States has historically been very hostile to new immigration. In the 1800s and early 1900s, opponents of immigration used diseases as a “scientific” justification for discriminating against immigrants. They associated particular national and ethnic groups with specific diseases. For example, Italians were accused of carrying polio, Irish were associated with cholera, and Jewish people were accused of carrying tuberculosis.

This association varied between the two coasts. Trachoma, a bacterial infection of the eyes, was associated on the East Coast with immigrants from Southern and Eastern Europe. However, on the West Coast, trachoma was seen as “peculiarly Asian.” Immigrants from Asia, especially Chinese and Japanese immigrants, were much more aggressively screened than other groups.