We keep hearing talk of the Coronavirus or Covid-19 but what exactly are viruses and why are they so problematic?

Prokaryotes

In the simplest of terms, viruses are what scientists call prokaryotes – single-celled organisms that don’t have a nucleus.  (A nucleus is the ‘brain’ of a cell, it controls the activities that take place within that cell.). There is much debate within the scientific community whether viruses should be treated as living organisms because they are dormant when they do not have a host in which to live.  Some viruses can remain dormant for thousands of years, if the conditions are right.  When I say they remain dormant, I mean that they cannot reproduce or feed or carry out any other metabolic process without a host.  

Genetic material

Viruses contain either DNA or RNA as their genetic material.  In humans and other mammals, the genetic material is a double helix of DNA.  In fact, the vast majority of organisms contain DNA as their genetic material.  Diseases such as Smallpox and Chickenpox are spread by DNA viruses.

Other viruses, such as the Coronaviruses and Rabies, are RNA viruses.  Conditions such as AIDS, transmitted by the viruses HIV-1 and HIV-2 which are also RNA viruses, but they are retroviruses, which means that the viral RNA incorporates itself into the host’s DNA (which was one of the reasons that this was so hard to treat in the early days of the disease, although thankfully, it is now very controllable).  

Parasites

In biology, the simple definition of a parasite is an organism that gains benefit at the expense of its host.  It logically follows that parasites want their host to survive for as long as possible.  Viruses are no different although we could all be forgiven for thinking that is not the case when we are in the depths of a pandemic, but in reality, it is rare for a virus to kill off a whole population.  Covid-19 is no different, it is not killing everyone.  In some people, the effects are very mild.  

There are lots of other pathogens (disease causing organisms) out there: bacteria, fungi, to name but two.  We live in a sort of harmony with most of them and we will continue to do so.

© Susan Shirley 2020