Viral Mutation: mutation is the worst thing that comes to our mind when we talk about pathogenic microorganisms.
In many Hollywood movies, you must have seen how a virus changes its form and creates a situation like doom.
Something similar is being seen these days in our world where a virus named SARS-CoV-2 has caused an epidemic and mutations are happening in this virus every day, due to which a new strain of it is being talked about.
There are also many strains of the new coronavirus that are more contagious and dangerous than the previous ones.
A mutation is a phenomenon that occurs in reality and is much more than a sudden occurrence in the lab. (The virus responsible for covid-19 must have mutated itself to be transferred from animals to humans) It is not necessary that the virulence of the virus always increases due to mutation.
Rather, when it comes to diseases caused by viruses, many times the mutated virus is no different from its original version. And sometimes there is also the possibility that the virus may lose all its ability to infect humans.
These days the new strain of the SARS-CoV-2 virus that has surfaced in the UK is being discussed the most and it is being said that this new strain has a very high ability to spread infection and due to this it can be a super-spreader.
By the way, in this article, we will discuss the frequently asked questions about viral mutations like – what is this mutation and why does it happen? Does the virus become more dangerous after a mutation and so on?
What is Mutation
A mutation, basically, is a change in the DNA sequence of an organism. Mutations can occur due to two reasons – either due to a mistake during cell division or due to exposure to a certain chemical, ionizing radiation or viral infection.
Whenever a living cell divides, it has to copy all its genetic material (DNA) into the new cell. DNA (deoxyribonucleic acid) codes for every single event that happens in our body.
The color of the skin, the color of the eyes and how strong the immune system will be, all these things are determined by DNA.
This process of replication is not completely accurate and there is a possibility of mistakes in it. If there is a change in the code of a gene, then that gene starts expressing itself differently or starts producing different types of proteins, or it stops expression completely.
If the protein plays an important role in certain metabolic pathways or certain vital functions of the body, the mutation may have an effect on phenotypic changes that can be observed physically.
For example – in the case of sickle cell anemia, a single mutation causes the gene to produce different types of proteins and thus shows up as sickle cell disease.
The good news, however, is that most (not all) organisms have a proofreading mechanism to prevent or neutralize these mutations once they occur.
Also, the mutation is not large enough to change the function of the gene itself. Even if this happens, different organisms (including humans) have pairs of genes of the same type.
Sometimes a mutation has to be present in both the pairs of genes in order to express itself or else this mutation remains in a hidden state.
The mutation that causes beta-thalassemia disease is an example of such a mutation. If any type of mutation occurs in a germ cell such as a sperm or an egg, it can be transferred to the next generation.
However, a mutation that occurs in any other cell of the body is not passed on to the next generation.
Mutation: What is the gene level mutation
Why do Virus Mutate
An organism mutates when it is subjected to evolutionary pressure – when it needs to evolve in order to survive. Viruses that have DNA as their genetic material do not mutate so quickly and have a very slow mutation rate – 1 mutation after making a few hundred or a few thousand copies.
On the other hand, RNA viruses such as the coronavirus and influenza virus mutate very rapidly – one mutation per copy.
The main reason for this is that there is a lack of proofreading in the process of making RNA copy – which is present in the process of DNA. When proofreading is not possible, mutations continue to occur and are passed on to the next generation.
Viruses also mutate due to physical or chemical changes, damage to nucleic acids caused by certain host enzymes, and failure to repair mistakes made after replication. Typically, mutations that do not affect the virus’s ability to infect host cells persist in a large population.
Studies suggest that the SARS-CoV-2 virus has a proofreading mechanism in its replication process, thanks to which many of its genomes have been preserved.
After Mutation does the Virus become more or less lethal
After a virus is mutated, it can be either more or less virulent and infectious. All organisms try to keep the mutation rate low because the risk of harmful mutations increases if there are too many mutations in each generation.
However, studies have shown that the more hostile an organism is placed in, the more likely it is to favor a mutation, as there is a greater chance that a beneficial mutation will occur.
RNA viruses typically have an advantage over mutations. Since the code for their own replication structure, they are able to adapt to some degree of adaptive use of mutations to maintain their fitness levels in different environments.
This is the reason why RNA viruses can change their host very quickly (e.g. from animal to human) and evade an immune response or become resistant to already effective drugs.
Sometimes mutations cause changes in the cell the virus is about to attack. However, in the case of RNA viruses that have a small genome, there is a high chance that mutations accumulate over time and reduce the virus’s pathogenicity, that is, its ability to cause disease, to the extent that The virus completely disappears from a certain population.
According to the researchers, the mutation rate (even if it is high) of the RNA virus is still within a range where it can be fatal for the virus – a concept called the error threshold. This makes the virus successful and possible despite the pressure of selection.
According to an article published in the peer-reviewed journal National Science Reviews, the SARS-CoV-2 virus has already evolved into two major types – the ancestral less infectious S type and the modified more infectious and virulent L type.
According to the study, L-type SARS-CoV-2 virus was present in 70 percent of cases in Wuhan, China and S-type in the remaining 30 percent.
Another study in China suggested that there have been about 30 mutations in SARS-CoV-2 so far. Lab studies suggest that there are some variants of SARS-CoV-2 that have the potential to generate a viral load 270 times higher than normal.
Do Virus Mutate due to changes in weather
This is probably the most common question that comes to the mind of most people and it comes to our mind considering the nature of seasonal flu. However, there is not enough evidence so far to say whether the virus mutates or changes its form due to changes in weather.
Influenza virus infection is most commonly seen in the winter season because schools have summer holidays (since the flu mostly affects children).
In addition, in winter, people are confined indoors and very close to each other – this can also be an important reason for the flu season in winter.
It is believed that the flu spreads in cold temperatures, but the flu is also seen in tropical areas where it is hot. Flu outbreaks are also seen in some areas during the summer months, indicating that the flu season has nothing to do with the cold season.
According to a study published in the journal Clinical Microbiology and Infection, the lack of vitamin D in the human body during the winter season leads to weakened immunity and thus causes respiratory viral infections.
If Virus Mutates will the Outbreak last longer
Studies have shown that there may be no truth to this. A virus, especially an RNA virus, can have multiple mutations within a single host.
However, in most cases, these mutations have a negative effect on the ability of the virus to infect new cells or replicate itself. Such variants are then removed through a natural selection process.
In RNA viruses, mutations may be frequent, but a mutation is selected only if it is in some way beneficial to the virus.
In addition, the virus has a number of properties – including its virulence and ability to spread from one host to another that needs to be preserved, in order to maintain the virus’s ability to survive.
These features are usually coded for by more than one gene and are therefore less likely to change. It is rarely seen when a virus changes its transmission mode in a very short time.
In the past, the flu outbreak was caused by a sudden single mutation in the influenza virus – called an antigenic shift.
However, the likelihood of such changes occurring in the flu is extremely low. Typically, flu viruses mutate regularly or sequentially – small mutations accumulate over time called antigenic drift.
Antigenic drift is the reason that causes new flu strains every year, for which a new flu vaccine is made every year. In contrast, a viral mutation (if it is sufficiently harmful) can completely stop an epidemic.
DNA: What is the importance of DNA copying in reproduction ?
If you contract and recover from one strain of the Virus, can you still contract another strain and fall sick?
Viral strains are genetically distinct variants of the same virus that result from mutations in the original virus. The new strain of the virus may be less infectious than another strain, or it may also have a mechanism that the host’s immune system does not catch.
If the host’s immune system does not recognize the new strain, there is a high chance that it can re-infect a person who has recovered from the original strain of the virus.
This happens frequently in influenza viruses. Dengue virus also has 4 different serotypes. Serotype differs from strain to strain.
A serotype refers to a group of organisms in a species that have the same type and number of antigens. On the other hand, there are both phenotypic and genotypic changes in the strain.
If a person is infected with one serovar of dengue virus, then he gets protection from the other three servers for a few months but after that, the person can get dengue infection from other strains.
The first infection with the dengue virus makes a person susceptible to a second serious infection and this is because of the existing antibodies that cause inflammation in the body.
Can two strains of the Virus be seen in one person at the same time
It is entirely possible that a person may become infected with multiple strains of the same virus at the same time. In the case of the influenza virus, this type of infection is the main reason for the development of new strains of the virus.
Suppose a person is infected with 2 different types of influenza virus, then the new strain will contain parts of the genetic material of both strains of the virus. Then this new strain will spread more rapidly.
Studies have shown that the swine flu pandemic (which began in Mexico in 2009) was caused by this type of strain. The strain responsible for swine flu contained a mixture of 4 different types of flu viruses – swine flu, human flu and bird flu.
Can Virus be killed? Why did SARS Outbreak end on its own
Viruses do not actually live. They are nucleic acids (DNA/RNA) that are wrapped in a protein coating. Viruses also contain lipids and many other substances.
When the virus enters a living cell, then it replicates itself and increases its number.
According to the US CDC, the virus is non-living outside a host, and some disinfectants containing ethyl and isopropyl alcohol in concentrations of 60 to 80 percent can inactivate most viruses.
Another way to kill or root out the virus is to improve the immunity of a population against a certain virus.
However, in order to develop immunity, you must first be infected with that virus or be vaccinated.
In the case of SARS, it is being said that due to contact tracing, robust testing and many other public health measures, the virus causing the SARS disease has disappeared.
Since the chain of transmission was broken (there are attempts to break the transmission chain for the SARS-CoV-2 virus as well), the virus could not spread much and disappeared.
However, experts suggest that the threat of SARS is still not completely eradicated and that it still exists and there is a possibility that the virus that causes SARS disease may mutate and reappear in humans.
Can the same medicine work if the Virus Mutates?
Drug resistance is of greater clinical importance when it comes to pathogenic bacteria, especially in viruses that mutate frequently. Most antiviral drugs target the way the virus replicates itself.
In cases where the right treatment is taken and the drug is successful in completely eradicating the virus from a certain population, resistance to the drug is unlikely to develop.
However, if the virus is not completely eliminated from the body, then there is pressure on the virus to escape the effect of the drug and become resistant to it.
In addition, studies also show that in some cases the virus population is in sync with its replication in such a way that new generations of viruses emerge when the drug concentration is lowest in the body. This process is called drug resistance by synchronization.
Specific mutations occur when they are needed and not all mutations are drug-resistant mutations.
A preprint study in India has suggested that the SARS-CoV-2 virus present in India has evolved in a different way than the strains present in the rest of the world. The virus spike has a unique mutation that acts as a target for the host antiviral RNA called hsa-miR27b.
According to the study, has-miR27b inhibits the replication process of HIV and this is the reason why anti-HIV drugs have been successful in India, while there have been conflicting reports about this drug in the rest of the world.
The study further states that this could also be the reason for the success of anti-malaria drugs in India.
Do Vaccines protect against most strains of virus?
Vaccines can be either monovalent (monovalent) which protects against a single strain of the virus or multivalent (multivalent) which protects against multiple strains of the virus.
For example- the measles vaccine is monovalent while the polio vaccine is multicomponent. Influenza vaccines that are made each year provide protection against all strains of the virus present in that year around the world. The flu shot for the year 2019 was quadrivalent, meaning it contained 4 strains of the virus.
Multivalent or polyvalent vaccines contain antigens from multiple strains. When our immune system comes in contact with these antigens through a vaccine, it produces antibodies against them, which protects us against the target germ.
