Decades of mass injections to treat schistosomiasis in Egypt apparently created the world's largest iatrogenic spread of a blood-borne pathogen—in this case, hepatitis C virus (HCV).
Since ancient times, Egypt has been home to extensive schistosomiasis transmission. In the 1920s, after injection of potassium antimony tartrate was discovered to be effective against the blood flukes that cause the illness, mass inoculation campaigns began in adults and children older than 6 years. These campaigns, in which millions of intravenous injections were given with inadequately sterilized equipment, continued until the 1980s, when oral medications became widely available.
Voelker R. HCV in Egypt. JAMA. 2000;283(14):1816. doi:10.1001/jama.283.14.1816