1847 North American typhus epidemic
The typhus epidemic of 1847 was an outbreak of epidemic typhus caused by a massive Irish emigration in 1847, during the Great Famine, aboard crowded and disease-ridden "coffin ships". In Canada, it is estimated that more than 20,000 people died during the epidemic.
Source: Wikipedia — 1847 North American typhus epidemic (CC BY-SA 4.0)