A Chinese immigrant in San Francisco fell ill with the bubonic plague in the first epidemic of the disease in the continental United States.

Bubonic plague is one of three types of plague caused by the bacterium Yersinia pestis. One to seven days after exposure to the bacteria, flu-like symptoms develop. These symptoms include fever, headaches, and vomiting, as well as swollen and painful lymph nodes occurring in the area closest to where the bacteria entered the skin. Acral necrosis, the dark discoloration of skin, is another symptom. Occasionally, swollen lymph nodes, known as "buboes", may break open.

The San Francisco plague of 1900–1904 was an epidemic of bubonic plague centered on San Francisco's Chinatown. It was the first plague epidemic in the continental United States. The epidemic was recognized by medical authorities in March 1900, but its existence was denied for more than two years by California's Republican governor Henry Gage. His denial was based on business reasons, to protect the reputations of San Francisco and California and to prevent the loss of revenue due to quarantine. The failure to act quickly may have allowed the disease to establish itself among local animal populations. Federal authorities worked to prove that there was a major health problem, and they isolated the affected area; this undermined Gage's credibility, and he lost the governorship in the 1902 elections. The new governor, George Pardee, implemented public-health measures and the epidemic was stopped in 1904. There were 121 cases identified, resulting in 119 deaths.