A virus is an infectious particle smaller than any bacteria. They are unique as they are only ‘alive’ and able to multiply inside the cells of other living things which are called hosts.
When found outside of a human, or host, they exist as a protein coat or capsid, sometimes enclosed within a membrane which can be spikey. All the time that they are outside of a host, their coat is being destroyed, which in turn means that they are being destroyed. They are not like bacteria or fungi which are able to independently grow and multiply on surfaces both inside and outside of the body.
The type of coat and shape of the virus will give it its name – coronavirus describes the crown of spikes on its outer membrane.
Inside the capsid is a core of genetic material, either DNA or RNA, which contains the genetic material for it to replicate itself.
There are many viruses, some examples are: Rotavirus targets the cells in the stomach and bowels giving the illness gastroenteritis, Hepatovirus targets the liver cells giving the illness hepatitis and Coronavirus targets lung cells giving the illnesses of flu and Covid-19.
Once the virus enters the host, it then finds cells that it can attach onto and once attached it then inserts its genetic material into that cell. This cell then stops doing what is should be doing and makes viruses instead. The virus can then leave in two ways, by budding or lysis.
In budding the new viral particle pushes against the host’s cell plasma membrane and sticks to it. The plasma membrane then wraps around the virus until it is fully enclosed – like a bud sticking out – and it is then released. This continues until all the host’s cell membrane is used up, and that cell dies.
In lysis, the virus particles burst out of the host cell resulting in the death of the cell.
The virus then goes on to find another cell, and the process starts all over again.
In relation to Coronavirus, there are two classes of lung cells that are affected – ones that make mucous and ones with hair-like batons called cilia. Mucus is needed in the lungs to help protect the lung tissue from pathogens and to make sure that they don’t dry out. The cilia cells beat around the mucus, clearing out debris like pollen or viruses.
It is thought that in Covid-19 the virus is killing off the cilia cells, which then means the airways are filing with debris and fluids and the mucus is not being spread around to help protect the lung tissue.
Covid-19 is the illness, the symptoms and signs, that result from the body’s immune system being activated and the direct damage caused by the virus as it replicates itself inside lung cells. The virus responsible for this is a Novel Corona Virus know as SARS-CoV-2.
Viruses only exist to make more viruses. They have no other agenda. They are not trying to make us ill, indeed killing us would no longer mean they had a host that enables them to replicate and hence be ‘alive’.
The symptoms we experience are a combination of the loss of lung cells and our body doing the right thing in trying to kill the viruses, via the immune response. This might explain why people are experiencing differing symptoms. It might be an indication of how good their underlying health is and how good their immune system is. We need to remember that an absence of disease or illness does not indicate that we are well – it just means that we are not ill enough to have been diagnosed with something.
This article was written by Karen Robinson, our Clincal Director.