Is the ultimate goal of the virus to kill the host or to coexist with the host?

Viruses are 100 times smaller than bacteria, which means their structure is much simpler. In fact, viruses are so simple that they only have a few proteins that encapsulate a piece of genetic information, and their genomes are very limited. The smallest viruses even have only a few genes, and the largest viruses generally do not exceed 200 genes.

The limited number of genes makes it impossible for all viruses to survive and reproduce on their own - generally speaking, only those who possess these two abilities (survival and reproduction) can be called living organisms, so there is a lot of controversy as to whether viruses can be considered living organisms.

The survival of viruses is completely dependent on cells. Both prokaryotic cells and eukaryotic cells can serve as hosts for viruses, and they can only multiply within host cells.

In other words, the cost for viruses to kill their hosts would be very high, because then they would not be able to complete their own proliferation, and they would not be able to survive independently after losing their hosts. Therefore, many people believe that the ultimate goal of viruses should be to coexist with their hosts, not to kill them.

In fact, the relationship between viruses and hosts is much more complicated than imagined, and the two cannot be summarized as coexisting and killing each other.

Simply put, a deadly virus does not necessarily become less virulent over time in order to coexist with its host.

In fact, during the transmission process, the virus can change in many ways. It can become more deadly or less deadly...

So, what do viruses really want to do? Is there any pattern to their spread?

The virus will indeed become more deadly

The epidemics in the "human world" in recent years have made us realize the horror of the virus, and have also attracted almost all of our attention, so many people may not know that this year there is also an unprecedented epidemic in the "poultry world".

Since October last year, avian influenza has broken out in dozens of countries around the world, and at least 3,000 poultry epidemics of varying sizes have been reported.

As of June, more than 77 million poultry had been culled due to infection with avian influenza, and at least 400,000 wild birds had died from this wave of avian influenza.

Since birds are migratory, they like to fly here and there, so the epidemic in the "bird world" is as difficult to control as it is in our world.

However, the culprit of this "poultry" epidemic is the H5N1 strain of avian influenza virus. Many people are probably familiar with this virus code name. It was first discovered in 1996 and has been spreading in the "poultry world" around the world for more than 20 years. There are reports about it almost every once in a while.

However, this year's mutant strain is considered to be the strongest in history - this avian influenza has been rated by many mainstream media as the most serious avian influenza pandemic in history.

It is obvious that this virus, which has been prevalent for at least 26 years, has no intention of coexisting with its host. On the contrary, it seems to want to kill its host.

In fact, in nature there are many cases where viruses are becoming increasingly unfriendly to their hosts, and those that can coexist harmoniously with their hosts are rare.

However, as we said before, viruses cannot multiply on their own, and cannot even survive outside host cells. There is a contradiction between the lethality of viruses and the possibility of their existence. Why would viruses become more deadly to kill their hosts?

The purpose of a virus is also to replicate itself

Although viruses are so simple that they only have a few genes, it is not difficult to find that the purpose of the existence of viruses, like all other life forms, is to replicate their own genes - this is the most essential need of the earth's "gene carriers" (all life and viruses).

When it comes to replicating genes, any gene carrier is the same. Replicating itself more and faster can make itself more competitive and less likely to disappear, because this will result in more offspring that can cope with different environments.

If the purpose of viruses is simply to replicate their genes more and faster, then there is actually not much contradiction between whether they choose to kill the host and whether they choose to coexist with the host.

Take the H5N1 strain of avian influenza virus, for example. At this particular moment, killing the host faster does not affect their replication efficiency.

For example: if the avian influenza virus is very deadly now, but it is spreading in an area full of hosts, then its choice to kill the host faster will not affect its ability to replicate itself at all, because it can quickly find a new host.

In addition, most viruses do not have only one host. They can infect many similar organisms. In this case, they can completely ignore the lives of some hosts.

This is true for many viral diseases that humans suffer from today, the most typical of which is rabies virus, which is 100% fatal to humans.

But for thousands of years, rabies viruses have never considered the lives of human hosts, and they have no reason to consider coexisting with human hosts because they still have many animal hosts in the wild.

In short, the virus will continue to mutate during the process of transmission. Among all these mutated strains, only the one that is most suitable for the current situation can quickly become dominant. This dominant strain is not necessarily the one that coexists with the host. It will only be the one that can replicate itself the fastest and the most at that time (under specific conditions).

at last

The spread of viruses is actually much more interesting than you might imagine. Although all viruses are unlikely to have brains, they will weigh how to spread in the best way for themselves.

In the process of spreading, they never put their eggs in one basket, they will keep jumping to other species to try new hosts;

There is also a most interesting situation. During the process of infection and transmission, viruses may directly merge their own genetic information with the host's genetic information, and the host will have new abilities after obtaining the virus's genes.

Have you ever doubted whether organisms can really evolve into different species simply through genetic mutations?

At least that's what Darwin thought. But the answer is obviously no.

Because the efficiency of gene mutation is too low, it is almost impossible for one species to evolve into another solely through gene mutation. It will simply become extinct first (because the speed of environmental change may be faster than this).

In fact, the fusion of genomes between different species plays a more important role in the process of biological evolution. At least 8% of the human genome comes from ancient viruses, and another 40% may come from viruses. It can be said that viruses live in our bodies.

The fusion of virus genes and host genes may be the most perfect coexistence between virus and host, but no one knows now whether this is the final destination of all viruses.

Source: Weird Luo