Virology in order to immunize others. In 1717 Lady Mary Wortley Montagu observed the practice in Istanbul and attempted to popularize it in Britain, but encountered considerable resistance. In 1796 Edward Jenner developed a much safer method, using cowpox to successfully immunize a young boy against smallpox, and this practice was widely adopted. Vaccinations against other viral diseases followed, including the successful rabies vaccination by Louis Pasteur in 1886. The nature of viruses however was not clear to these researchers. In 1892, the Russian biologist Dmitry Ivanovsky used a Chamberland filter to try to isolate the bacteria that caused tobacco mosaic
Smallpox the first use of the term "variola"; other historians speculate that Arab armies first carried smallpox from Africa into Southwestern Europe during the 7th and 8th centuries. In the 9th century the Persian physician, Rhazes, provided one of the most definitive descriptions of smallpox and was the first to differentiate smallpox from measles and chickenpox in his "Kitab fi al-jadari wa-al-hasbah" ("The Book of Smallpox and Measles"). During the Middle Ages, smallpox made periodic incursions into Europe but did not become established there until the population increased and population movement became more active during the era of the Crusades. By