Viruses are funny things. So small that they won’t appear on all but the most powerful microscopes, yet powerful enough to bring down the mightiest of humans. What’s even stranger is the fact that they can be so different from one another; from a (relatively) harmless cold to a life-changing HIV infection to the recent coronavirus pandemic, it begs the question – what makes a virus so unique?
First things first, not all viruses look the same. Some are ball-shaped, some are cylindrical and others are formed by a combination of shapes. The latter often look like the Apollo moon lander, with spindly legs and a pod at the top. Despite first impressions, this shape isn’t a good indicator of how dangerous a virus is, in fact simple is sometimes more effective – just take a look polio, a tiny sphere shaped virus that caused lifelong disability in the UK as recently as the 1960s.
More important than the overall shape, are small structures attached to the surface of the virus. These act as landing gears of sorts, sticking out like the seeds of a dandelion plant. When they come into contact with a human cell, they help the virus to latch onto its surface. These structures, called antigens, are a gift and a curse – helping the virus carry out its nefarious task but making them immediately recognisable to our own immune systems. It’s an ID card of sorts, and viruses like the common cold keep popping up time and time again due to the fact that they can change the shape of their antigens from year on year – the equivalent of drawing a little moustache and glasses on a driving licence photo.
It’s important to note that the outside of the virus is made of the same kind of molecules as our cells. This allows them to fuse and release their contents into the inside of the cell, like a drop of water when it touches the surface of a lake. The more complicated viruses are sneakier and inject their contents through the surface in the same way a mosquito would. Either way, when the contents make their way inside you can be sure things are about to kick off.
Every cell has a full set of DNA, a set of instructions that make you unique (unless you’re a twin). These are carefully stored in the heart of the cell as long ribbons, condensed in a similar way an old-school cassette tape would be. Viruses work by cutting these sections of DNA, sneakily inserting their own, then stitching the whole thing back together. Unknown to the cell, it mindlessly starts to read these instructions, only this time they include the command to make something new – the parts needed to make more viruses.
Eventually, these parts assemble and move out the cell, stealing a piece of the outer cell to act as clothing. Repeated enough times, the cell begins to shrivel until it is put out of its misery. The army of new viruses then goes on to repeat the process. It’s this cell damage that leads to the symptoms you feel, like a rough throat for example.
Viruses can carry a few kinds of instructions, either DNA or a different kind of messenger known as RNA – this gets converted into DNA in the cell. The latter kind is known as a retrovirus and, because of this extra conversion step, doesn’t always insert an exact copy of the intended DNA. This results in viruses that are much more likely to mutate, meaning that HIV, for example, is incredibly resistant to traditional treatments.
Other important things are the amount of DNA/RNA being carried, the types of enzymes (tiny molecular machines that snip and insert the instructions) and whether or not a virus can lie dormant in cells, just waiting for the perfect time to strike.
As any real estate agent will tell you, it’s all about location, location, location. This is especially true when it comes to the symptoms a virus can cause. Many viruses thrive in the warm stable environment of the lungs and throat, giving rise to coughing, wheezing and all-round sniffles. These tend to be common due to the fact they can be spread in the air and can easily find their way around the office during the winter flu season. Other viruses can affect the nervous system (viral meningitis), or the ear (labyrinthitis), or almost anywhere for that matter. These will all bring their own set of symptoms, which a doctor can use to help identify the culprit.
Once exposed to a viral antigen, a kind of white blood cell called a ‘B-cell’ gets to work on creating the antidote – tiny molecules called antibodies. These are specifically shaped to match that of the antigens on viruses, and can be used to clump them together, hinder their ability to act, or tag them for destruction by bigger specialised cells.
Once the right antibody has been created it’s only a matter of time for the virus. The B-cells can replicate rapidly and produce antibodies at a scarcely believable 2,000 molecules a second. The fighting between viruses and the immune system results in the inflammation commonly seen with infections and is simply a way of allowing more cells to join the fight. At this point, you’re likely on the road to recovery and after a few days, symptoms should begin to fade away.
HIV falls into a category of its own as it specifically targets the white blood cells themselves, hiding within them and slowly weakening the immune system over time. Drugs called antiretrovirals are often used for this and other retroviruses that are hard for the body to combat. There are many different kinds and they all work in different ways. They are often used together to make sure they are at their most effective.
Unlike bacterial infections, you cannot treat a virus with antibiotics. In most cases of viral infection you should simply give your body the ideal conditions to develop its own defences. However, if symptoms are serious or someone has a weakened immune system due to medication or age then medical advice should be sought as soon as possible.
Vaccination Q: What’s better than getting treatment for a virus? A: Not having one in the first place of course.
Vaccines work by introducing the viral antigens into the body in small amounts (often the virus is either dead or not included in the vaccine), allowing the body to develop antibodies without the pain of infection. When the real virus actually turns up, the body doesn’t have to spend time developing a solution. Instead it ‘remembers’ the infection and can destroy it before it has time to cause any damage. It’s a simple principle, but astoundingly effective. Indeed, diphtheria, whooping cough and smallpox are all confined to the archives of history (or the freezers of very secure laboratories) thanks to the wonders of viral vaccination. In the case of Coronavirus, or Covid-19 as it's otherwise known, there is no vaccine. However, researchers are working on developing a vaccination, which can take months before it is even ready for clinic trials on humans.
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