What type of ‘creatures’ are pathogens?
EBOLA, bird ‘flu, SARS, swine ‘flu, AIDS, the common cold, influenza, polio, chickenpox, measles, mumps and a host of other common diseases are caused by viruses so we are well familiar with these pathogens but what kind of ‘creatures’ are they?
Debate continues as to where the thousands of viruses that have been identified belong in the great scheme of things. Some authorities maintain they are primitive life forms. Others dispute that they are alive at all and classify them as non-living ‘particles’, ‘agents’ or ‘entities’ that went down an evolutionary cul-de-sac in the very early days of the development of life on Earth.
While viruses appear to be alive in that they can grow, have genes and can reproduce, they are incapable of surviving on their own. They need a host to support them. They failed to evolve a cellular structure of their own and need to get inside the cells of a host plant or animal to survive. If they end up outside the bodies of plants and animals for a prolonged period of time they die.
To say they failed to develop a cell structure may be a negative way of perceiving them. The alternative perception is that they succeeded in evolving to infiltrate the bodies of other life forms including bacteria thereby ensuring their survival.
Fossil viruses have never been found so their origin is unclear. They have very simple bodies and are capable of mutating or undergoing change very rapidly so the strain of virus that presents itself this year may not be the same strain as that of its ancestors that presented last year or five years ago.
And to add to that cocktail of complicating factors they are extremely tiny in size: the typical virus is about 45,000 times smaller than the width of a human hair. However, what they lack in size they make up for in numbers; viruses are the most abundant biological entities on Earth in terms of absolute numbers.
Many viruses damage their hosts to the point of causing death and so they must move on to find a new host. We are all too familiar with the sights on TV of people clad in PPE coverall suits in west Africa burying victims of the deadly Ebola virus while trying to protect themselves from infection and stop the spread of these extremely tiny but extremely dangerous pathogens be they creatures, particles, agents, entities or whatever.
The ‘flu virus has a striking body shape with spikes of proteins and sugars arising from a spherical envelope of fat.