BRITISH immunologist Peter Medawar once stated, "viruses are a piece of bad news wrapped up in protein".
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It's a justifiable statement given the current viral pandemic. These tiny particles, around a millionth of a millimetre in size, can bring the world to its knees.
Viruses are certainly copping a lot of bad news lately. The havoc they can wreak on human society is a recurring problem throughout human history with breakouts of, to name a few, measles, mumps, smallpox, and polio, and since 2000, SARS, swine flu, Nipah, MERS, Ebola, Zika, bird flu, Hendra, HIV, and various influenza strains.
The threat of disease transmission is heightened as the interface between humans and our environment is increasingly compromised leading to many cases of viral 'spillovers' from animals to humans.
Viruses have been evolving since 'deep time' and it has been suggested that they were around before the single-celled and multicellular organisms took different evolutionary paths. Some researchers even theorise that they were around before DNA - that is many billions of years ago. Suffice to say the viruses are here to stay.
Viruses are found everywhere, occupying every niche imaginable from hydrothermal vents and acid lakes, to the innards of bacteria.
They are also incredibly diverse and abundant being the most numerous microbes on Earth and this includes the oceans where there are an estimated 10 billion viruses per litre of sea water!
Billions of viruses from different viral families are just getting about their business, but some are implicated in many human, animal, and plant diseases. What is not always acknowledged is that they play a key role in maintaining life on Earth.
An astonishing example is the viral killing of an estimated 20-40 per cent of marine bacteria every day and the rapid reduction of phytoplanktonic algal blooms. Phytoplankton produce almost half of the world's oxygen and are integral to the marine food-web. Algal blooms, however, can produce extremely toxic compounds that are harmful to marine life and humans.
While the Covid lock-down has changed our behaviour, infected animals can also change behaviourally - we all know the stories of Rabid dogs. Virus-host interactions are part of the evolutionary scheme of things and are not always so lethal. It is known, for example, that some birds infected with avian influenza have altered feeding and migratory patterns - behaviour that affects populations.