HISTORY OF VIROLOGY The term virus has been used in medical texts since 1599, when the term actually meant “venom”. Primitive vaccination has existed for thousands of years in China where vaccination was called variolation. The process involved mixing body fluids from those with smallpox with those who did not have the disease in order to immunize those uninfected. This was further advanced in the western world in the late 1700s, when cowpox was used instead to immunize patients against the related smallpox vaccine. Rabies vaccines have existed since 1886, even though viruses themselves were unknown entities. Viruses were attempted to be extracted since the 1800s. Biologist Dmitry Ivanovsky demonstrated that filtering leaf extracts from tobacco plants that had been infected with the tobacco mosaic disease did not trap the infectious agent. It was then proposed that a very small particle or toxin was involved in these types of infections. Others determined that the filterable substance was able to be passed from one generation to another and that it was infectious rather than toxic in nature. The first suggestion that viruses were cancer-causing happened in 1903 and was essentially proven a few years later when a virus-like agent was found to transmit chicken-related leukemia. It was nearly at the same time when chicken sarcoma was found to be infectious in nature. This was caused the Rous sarcoma virus 1—later found to be a type of retrovirus. While we don’t think of bacterial viruses, called bacteriophages, affect humans but they do in fact have an impact on us. The first bacteriophages were recognized in 1911 and, because bacteria grow easily, the understanding of these infections has helped the study of virology overall. It was later determined that, while scarlet fever is bacterial in origin, it depends on one that is itself infected with a bacteriophage. Animal virus research was expanded greatly when it was discovered that these viruses could infect chicken eggs. This fact has since led to the development of many vaccines against human viruses, such as the influenza virus vaccines. Yellow fever vaccine came
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