Viruses were first discovered at the end of the 19th century, although the symptoms they cause were identified much earlier. One of the earliest pieces of evidence is the symptoms of poliomyelitis in an Egyptian priest depicted on a hieroglyph.
VIRUSES
Introduction
Viruses were first
discovered at the end of the 19th century, although the symptoms they cause
were identified much earlier. One of the earliest pieces of evidence is the
symptoms of poliomyelitis in an Egyptian priest depicted on a hieroglyph. Virus
discovery came about when the cause of an infectious disease (rabies), could
not be explained by the presence of bacteria. Unlike bacteria, the ‘infectious
materials’ were not retained by filtration and thus viruses were then referred
to as ‘filterable agents’ or ‘filterable viruses’. Until the advent of electron
microscopy in the 1940s, only the chemical nature of viruses (i.e. proteins and
nucleic acid) could be identified and their infectivity was mainly studied in
animal models. The observation of a virus by electron microscopy and the
development of cell tissue culture started the golden era of virology. Since
then a large number of viruses have been isolated, their structure identified
and their replication understood, leading to the design of potent antiviral
drugs and effective vaccines. Progress in virology over the last 50 years have
been considerable, leading to the eradication of smallpox following a worldwide
vaccination programme, and the likely future eradication of poliovirus. For the
first time in human history an infectious disease has been vanquished. Despite
such an achievement, much progress is still required to combat other viruses.
For example, despite large financial investment and high profile studies, a cure
or vaccine for HIV is still not available. The number of commercially available
antivirals is also still limited, when compared to the number of antibiotics.
Within the last few years, diseases caused by viruses in human and animals have
reminded us that viral infections can easily spread and cause epidemics and
pandemics. Recent examples are ‘swine flu’ and ‘avian flu’, both caused by
influenza viruses, and also an outbreak of severe acute respiratory syndrome
(SARS), the virus originating from Asia and spreading worldwide, and outbreaks
of foot and mouth virus affecting cattle, sheep and pigs that had important
economic consequences in the UK and mainland Europe.
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