History of Virology

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

out of chicken egg research and has since saved the lives of millions who would have become infected throughout the world.

The tobacco mosaic virus was the first to be crystalized so that its structure could be analyzed using electron microscopy as of 1935. It was since shown that the virus was still infectious after it had been crystalized, further showing that these were not truly life forms. The self-assembly of viruses was later demonstrated in 1955, although it was only proposed at the time that this was what happens inside cells.

The first retrovirus was discovered in 1965, which is an RNA virus that is reverse transcribed to make complementary DNA that potentially could integrate into the host’s genome. Infectious human retroviruses were first discovered in 1974 and the role of reverse transcriptase in these infections was uncovered. It was only later discovered that reverse transcriptase is not an enzyme specific to these viruses but that it also is a part of the physiology of retrotransposons in eukaryotic DNA.

Cancer research as it applies to virology became clarified in the mid-1970s when it was discovered that not all cancers from viruses were because of viral oncogenes. Instead, some viruses, including the Rous sarcoma virus, also activated proto-oncogenes within the genomes of eukaryotic cells. The proto-oncogene was found to turn into an oncogene in order to lead to cancer.

While viral outbreaks had been seen for a very long time, the first Ebola outbreak began in 1974 as an emerging or novel viral infection. Five years later, the World Health Organization announced that smallpox had been eradicated worldwide. Prions as infectious agents were discovered in 1982 and the HIV virus was first reported as an infectious disease in 1981. HIV has become the best-studied virus in the world. This has led to the first antiretroviral drug treatments for the disease.

Gene therapy has been studied with regard to viruses since the 1980s. This came at the same time that it was determined that retroviruses were able to insert themselves into the human genome. The success of this therapy is not yet what is probable in the future, although a few patients with severe combined immunodeficiency disease or SCID have been successfully treated with viral vector-based gene therapy.