The mention of mutation is enough to give us nightmares of viruses that evolve with the sole aim of killing mankind and taking over the earth.
“But in reality, a virus’s main purpose of mutating is to seek coexistence with the human body. A virus mutates for survival, not to kill. It tries to adapt to the conditions of the human body,” explains Dr Kenny Voon, a virologist and lecturer at the International Medical University (IMU).
“Humans are a reservoir for the virus. We help it to propagate more. It doesn’t want to kill us, the host. If the host dies, there is no co-existence. This is why its main aim is not to become more deadly,” he adds.
He explains that when a virus first jumps from one species to another we often see a high death rate. This is because the virus has not learnt to live within its new host. “For example, the common cold was probably a virus that started infecting humans a long time ago and now it just coexists with us,” he says.
“Laboratory results, from a study that compared infectivity and virulence of emerging SARS-CoV-2 variants in Syrian hamsters, show that while the COVID-19 virus has become more contagious, it has not become more deadly,” he says, although he does warn that this is an inference made from laboratory testing. How the virus affects people in the real world can be different.
A case in point is the Delta (Indian) variant. This variant has been speculated to be more deadly because there have been more cases of death reported. However, in laboratory tests, the variant did not show up to be more deadly. “We will only know once we have more data from community samples,” explains Dr Kenny.
Roadmap of a virus
Dr Kenny also sheds some light on the journey of the COVID-19 virus from bats to humans. He explains that the original virus in a certain species is called an “ancestor virus”. When a virus jumps from another species into humans it is called an “outbreak virus”. For example, the COVID-19 virus is an outbreak virus while the ancestor virus has been found to be a coronavirus carried by bats.
However, in between the ancestor and outbreak viruses, there has to be a “progenitor virus” that has allowed the virus to make that jump. For example, in MERS, the link or progenitor virus came from camels, while the Nipah virus in Malaysia was passed through pigs.
In our current pandemic, the bat coronavirus (identified as RaTG13) carries 96.2% of the same genetic sequence as the COVID-19 virus (SARS-CoV2 Wuhan) in humans, leaving a significant 4% that is different. “The virus may have been propagating in another intermediate host before jumping into humans but we have not been able to identify that progenitor virus yet.”
Now that the virus has jumped into humans, the next step is for it to mutate in order to adapt to our bodies.
There are two ways a virus can mutate. One is called a point mutation, where at a certain point in the genetic sequence, the amino acid changes into another amino acid.
The other is through recombination. Recombination happens when a part of a virus joins up with a part of another virus. For example with the MERS virus, it was found that a part of the MERS-CoV lineage 2 combined with the MERS-CoV lineage 4 to become another strain, namely the MERS-CoV lineage 5. “This can only happen if both virus strains infect one host,” explains Dr Kenny.
Are there factors that make it more likely that a virus will mutate? “We cannot pinpoint what factors induce mutation as there are too many variables,” he says.
Concern vs Interest
The mutation causes changes in the genetic sequence which affects the behaviour of a virus. Unlike horror movies, the virus does not have a brain that tells it to mutate in one way or another. It is a process of trial and error that can sometimes make a virus stronger, or make it decrease in function.
According to Dr Kenny, when we analyse the behaviour of a virus we are looking at three main areas: transmissibility, virulence and antigenicity. This translates to how contagious it is, how deadly it is and if the virus will escape the vaccines available.
You might have come across the term variants of concern (VOC) when reading about the virus mutation. A variant of concern is when the mutation has changed the way the virus behaves in one of the three areas. The Alpha, Beta, Gamma and Delta variants — or more commonly known respectively as the UK, South Africa, Brazil and Indian variants which are the current four variants of concern because enough data has been collected to show that the virus has changed behaviour in either transmissibility, virulence and antigenicity. Malaysia has now recorded three out of the four variants of concern.