the fight against coronavirus
Updated: Mar 28, 2020
A newly-identified virus has rapidly spread from a market in the city of Wuhan in China to over 25 countries. Sadly over 400 people have died due to infection, which although suggests a lower mortality rate than implied by some sensational reports of the 'deadly' virus, there could be implications for health systems if large populations become infected. Fortunately, scientists from across the globe have combined efforts to arm themselves with knowledge about this virus in an effort to reduce its mortality rate or slow its spread. This is the first time scientists have worked together at this speed and on this scale, sharing breakthroughs such as sequenced coronavirus genomes on portals for anyone to access and sending virus particles between labs so they can be studied in the lab.
But what knowledge do we actually need to help fight coronavirus?
First, a quick step back - what is a virus?
Viruses are not technically living, which makes our defence strategy against them quite different from other microbes like bacteria. Rather than being made of cells, they are simply genetic information (either DNA or RNA) coated in proteins, and are therefore much smaller.
Outside cells viruses are completely inanimate, they don't do anything. Once they get into a cell, however, their tiny amount of proteins and genetic information are sufficient to hijack the inner workings of the cell, tricking the cell into producing more viral particles, often until the cell dies and the new virus particles are released.
This means there are 3 weak points at which we can fight against viruses:
1) Stop the virus being transmitted in the first place
2) Stop the virus entering cells
3) Stop the virus from causing harm once it has infected cells
Not to scale.
Step 1) Stop the virus being transmitted in the first place
To slow down the spread of the coronavirus, we need to know how it is spread. A diagnostic tool that looks for the RNA in the coronavirus is helping researcher's understand how quickly the virus is spreading and between which patients. The genetic material of the virus has also been important to identify which family it belongs to - the coronavirus family. This family of viruses causes respiratory infections and includes the virus that causes SARS. By checking samples from the different parts of the body, it seems that the virus is found in the oral cavities, so might be spread by respiratory droplets which come out when you sneeze or cough. These preliminary results have informed protection advice, such as to cover mouths when coughing.
All viruses in the coronavirus family originally come from non-human animals. Knowing which animals are the source of the virus means we can avoid more humans getting infected from animals. A common technique in biology is to compare different genomes to see how similar they are. This is done on a computer by just aligning the sequences and then checking how many nucleotides they have in common.
The sequences are just illustrative. 4 nucleotides of DNA are represented by A, T, C and G. For coronaviruses proteins have also been aligned.
We assume that sequences that are very similar are closely related, as they haven't had enough time to evolve to become different from each other. Using this technique, a group of scientists from China found that the coronavirus is very closely related to two viruses in bats (sharing about 90% of all the nucleotides in their sequences), suggesting that this animal is the potential source of the virus. It is likely that there was an intermediate animal between bats and humans (likely one sold at the Wuhan market) and the hunt is still on to identify what animal this might be.
Step 2) Stop the virus entering cells
Viruses need to 'dock' onto the surface of cells before they can enter them. They do this by attaching to receptors on the surface of cells. All of the cells in your body are covered in receptors, which are important for lots of things like letting them sense what's going on in their environment and communicate with each other, and viruses take advantage of them to gain entry. Fortunately human cells have developed their own weapons: antibodies. Antibodies are Y-shaped proteins that are made by your immune cells. Once they find a microbe (bacterial or a virus), they stick to it so it can't enter cells and at the same time alert other immune cells to come and destroy the virus. The most impressive thing about antibodies is that they come in all sorts of flavours, which recognise and stick to all sorts of microbes. If a new microbe enters the body there won't be any antibodies against it yet, but once the antibodies start being made your body will be able to recognise that particular microbe and you will be 'immune' to it (that’s why you only get chickenpox once).
Vaccines make use of this natural defence mechanism to 'prepare' your body for attack using a harmless bit of the virus so that you make antibodies against it and become immune to the real thing. Vaccines usually take years to develop, but for the coronavirus scientists are trying to speed up the process to respond to the outbreak. Huge amounts of funding to various pharmaceutical companies and academic groups is helping accelerate this process, which is being approached at different angles (e.g. different virus bits to use, different ways of delivering them, etc.)
Step 3) Stop the virus from causing harm once it has infected cells
Some antiviral drugs work by stopping the virus once it infects cells. For example, the antiviral drug acyclovir works against herpes and chickenpox infections by acting as a Trojan horse. When the virus tries to replicate itself in the cell, it accidentally uses acyclovir instead of G to make its DNA. Due to the shape of acyclovir, no more nucleotides can be added and the whole process gets stuck, meaning no new viruses can be made. In a similar way, researchers are using their knowledge of coronavirus' family members and the virus itself growing in labs to see if they can find any weak points to attack the virus once it's inside cells.
New viral outbreaks can catch us by surprise and cause panic when there are no treatments. Due to our understanding of how viruses work, however, researchers are able to explore lots of potential routes to try to slow its transmission and reduce the effect it has on infected patients. Usually it takes years to make effective medicines; but thanks to the hard work, collaborative efforts and transparency of research groups and health departments it looks like there is hope we will have our weapon against the coronavirus in the near future.