How deadly cholera pandemics transformed modern Iran. Pandemic cholera reached Iran for the first of many times in 1821, assisted by Britain's territorial expansion and growing commercial pursuits. The revival of Iran's trade arteries after six decades of intermittent civil war, fractured rule, and isolation allowed the epidemic to spread inland and assume national proportions. In A Modern Contagion, Amir A. Afkhami argues that the disease had a profound influence on the development of modern Iran, steering the country's social, economic, and political currents. Drawing on archival documents from Iranian, European, and American sources, Afkhami provides a comprehensive overview of pandemic cholera in Iran from the early nineteenth century to the First World War. Linking the intensity of Iran's cholera outbreaks to the country's particular sociobiological vulnerabilities, he demonstrates that local, national, and international forces in Iran helped structure the region's susceptibility to the epidemics. He also explains how Iran's cholera outbreaks drove the adoption of new paradigms in medicine, helped transform Iranian views of government, and caused enduring institutional changes during a critical period in the country's modern development. Cholera played an important role in Iran's globalization and diplomacy, influencing everything from military engagements and boundary negotiations to Russia and Britain's imperial rivalry in the Middle East. Remedying an important deficit in the historiography of medicine, public health, and the Middle East, A Modern Contagion increases our understanding of ongoing sociopolitical challenges in Iran and the rest of the Islamic world.