Longest incarceration for an asymptomatic carrier
"Typhoid" Mary Mallon
26 year(s)
United States (North Brother Island)

The longest period of enforced isolation for an asymptomatic disease carrier is 26 years, served by "Typhoid" Mary Mallon (USA, b. IRE) on North Brother Island, New York, USA, between 1907 and 1938 (one stretch from 1907–10, then another from 1915–38).

Mary Mallon was employed as a cook in Long Island, New York in 1906. She was a "healthy carrier" of the infectious disease typhoid, Salmonella typhi, and denied being ill. Mallon worked for a wealthy banker, Charles Henry Warren, and managed to infect more than half of the household with typhoid.

The source of the infection was not obvious at first, and it was not until a sanitary engineer named George Sober was engaged by the Warren family that suspicion fell on Mary Mallon. Sober discovered that Mallon had cooked for eight previous families, seven of whom had experienced cases of typhoid. Mallon did not exhibit any symptoms herself, and appeared healthy.

In 1907, around 3,000 New York residents caught typhoid and Mary Mallon is assumed to have been the origin for that epidemic. Mallon tried to hide from health officials but was later quarantined against her will in Riverside Hospital near New York. Doctors made a number of ineffective attempts to cure her, including with laxatives and brewer’s yeast. Mallon was initially incarcerated for two years, and was briefly freed by a new health commissioner in 1910. However, she continued to infect people and she was soon incarcerated again at Riverside Hospital for the next 23 years until her death in 1938, following a stroke.