4. Typhoid

From the New York American, 1909. Image from Wikimedia Commons.

Typhoid, a bacterial infection that leads to a high fever, spread to New York in waves starting in the 1840s until the early 1900s. Between 1847 and 1848, nearly 2,400 New Yorkers died of typhoid, and the disease killed over a thousand New Yorkers in 1851, 1864, and 1865. By the early 1900s, however, typhoid became much more serious once Mary Mallon, known as “Typhoid Mary,” began infecting New Yorkers without even realizing it.
Emigrating to New York in 1883 as a teenager, Typhoid Mary, who was born in 1869, worked as a chef for numerous families in New York City and Long Island despite being an asymptomatic carrier of typhoid, which means that she could spread the disease without experiencing any symptoms. Typhoid Mary supposedly infected at least 51 people and was quarantined on North Brother Island in the East River for the last 23 years of her life. Although she only spread the disease to what seems to be a small number of people, she became the face of the epidemic in New York. By 1914, a typhoid vaccine was developed and licensed.