Born in Cookstown, Co. Tyrone, Mary Mallon emigrated to New York where she was employed as a domestic assistant.

However, Mary had a great talent for cooking and ended up working as a cook for many affluent families in the New York area.

But a strange pattern started to occur. Anywhere that Mary worked, family members in the household started to develop typhoid fever.

Mary was unaware that she was carrying the bacterial infection and in 1907 she was the first person in the United States to be identified as an asymptomatic carrier (showing no symptoms) of the bacteria associated with typhoid disease.

This is part of the History (Environment and society) section of BBC Bitesize Secondary (KS3) level. For more Bitesize content head to bbc.co.uk/bitesize

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