Al-Razi on Smallpox and Measles

This article by Dr. Abdulnasser Kaadan shows that as early as the 9th century, the well known Muslim physician al-Razi described, in his book Kitab al-Jadari wa 'l-Hasba (The Book on Smallpox and Measles), the symptoms of smallpox and measles. Furthermore, he distinguished between the two diseases, using an antecedent of the modern differential diagnosis.