Viral myths – a dose of reality

As I listen to non-scientists (politicians, journalists etc) talking about the pandemic and vaccinations I am constantly struck by how generally misunderstood viruses are.  Most people seem to imagine a virus as a very small ‘bug’: some kind of really, really minute insect that gets its way into us because that is what it wants to do.  In reality, a virus is not even alive; it is more akin to a minuscule piece of machinery.  It is just a string of genetic code (in the case of SARS-Cov-2, to give it its official name, a strip of mRNA) with some spiky-shaped proteins around it.  A virus has no arms or legs, no fins or wings.  It cannot run or fly or swim or even wriggle; it cannot move itself.

A virus particle sitting on a surface such as a table or chair is incapable of harm.  To do us any harm the virus particle has to get into our airways – or, more accurately, has to be got into our airways.  It has no means of getting anywhere by itself.  That means we have to move it, by spraying it into the atmosphere (coughing, sneezing or just talking) so someone else can inhale it, or by picking it up on our hand and transferring it to our eyes, nose or mouth.  The virus cannot spread itself – WE have to spread it.  Therefore, we also have the power not to spread it, if we choose.

Once we have spread it into our airway a virus particle may bump into an ACE-2 receptor on the surface of a cell.  As its name suggests, this is a receptor which is shaped just right for a molecule of Angiotensin Converting Enzyme 2 to fit into.  It is the cell’s way of fishing for ACE-2.  Once a molecule fits into it the receptor automatically starts a process of transporting the molecule inside the cell.  Unfortunately for us the tip of the spike protein on the outside of the virus particle is similar enough to the end of the ACE-2 molecule that it fits the receptor well enough for the cell to be fooled into reacting as though it had caught some ACE-2 and so the cell takes in the virus particle.   Once the cell has the virus particle inside it, it does exactly what it always does with scraps of genetic material: it processes it and makes whatever is coded in it.  In this case the genetic code contains the instructions for making the virus, so the cell becomes a virus manufacturing factory.

The second misconception seems to be that if I don’t feel ill then I’m not infected.  One of the problems we have with this virus is that everyone who gets infected has a period (of about two days or so, we think) of being infected and infectious (i.e. spraying virus particles over everything and everyone as we speak) while feeling absolutely fine and having no symptoms whatsoever.  Even having a negative test result does not mean that you are not infected.  It could mean:

  1. You weren’t infected when the swabs were taken, but you have been infected in the time it has taken to run the test;
  2. You were infected when the swabs were taken, but not for long enough yet to build up enough viral load to be shedding enough virus for the swabs to pick up sufficient to get a positive result;
  3. You were infected when the swabs were taken and you were shedding enough virus but the swabs were not taken well enough to pick up sufficient virus to get a positive result;
  4. You were infected and the swabs did pick up enough virus but something went wrong during the test and it returned a ‘false negative’ result.

The reality with this virus is that we never know we are infected until it is too late: we will have spent at least a couple of days infecting other people by the time we find out we have got it.  The ONLY way we can avoid infecting other people is by wearing an effective mask (I would say a FPIIR surgical mask as a minimum) to stop most of the virus escaping from our nose and mouth, and by staying away from them.  We have to act on the assumption that we are infected, all the time: even when we get a negative test result.

The third major misconception is that vaccination stops you getting infected.  It doesn’t.  Vaccination prepares our immune system, so it behaves differently once we do get infected.  We still get the virus, it’s just that our immune system responds fast enough that we don’t get ill with it (or at least not seriously ill).  What we don’t yet know is whether the vaccines get our immune system to work fast enough to stop us spraying out virus and infecting other people: in the case of the Oxford vaccine it seems to have a significant effect on the original strain, but we don’t yet know about the more recent strains.  We do know that it takes time (probably two to three weeks) for the vaccine to ‘train’ our immune system to recognise the virus and that it takes a second dose given a few weeks after the first to get the maximum effect.

This means that the day after we have been vaccinated, we have no more immunity than we had the day before we were vaccinated. We need to carry on with the same precautions for several weeks at least, to avoid getting ill.  Even after that, even if our immune system is good enough to stop us getting ill with the virus, we will still be able to get it and may be able to pass it on to others without ever knowing we had it.  Once we have been vaccinated, we need to be just as vigilant about the risks of infecting other people.  The vaccine merely reduces (massively) the risk of being seriously ill and needing hospital care.  The purpose of the vaccine programme is to protect the NHS from being swamped.  It does not necessarily stop the virus circulating – and mutating.

The vaccination program does not mean the virus will be gone and everything can return to how it used to be.  It is an essential first step, but we have an awful lot more to learn about this virus and its mutations before we will be able to think we have it ‘under control’.