Human, nature and virus: who is the enemy and who is the ally?
Viruses require a living cell to reproduce. Because viruses cannot produce the proteins they need. Therefore, viruses are obligate cellular parasites. They break out of the infected cells and spread out to find new cells. In this sense, the name Virus means poison in Latin.
For humans, viruses have become synonymous with influenza, AIDS and, ultimately, the Covid-19 pandemic. Therefore, they now consider viruses as the eternal enemies of humans. For almost the last two years, Covid-19 has caused the death of millions of people all over the world and caused great economic damage.
How do viruses make humans so helpless? Are we facing viruses or nature? Who is the enemy, and who is the ally in the triangle of human, virus and nature? In order to find answers to these questions, we need to discuss the many functions of viruses in nature. But here, we will focus only on one function in particular.
Viruses play an important role in the conservation of biodiversity. Below a certain concentration threshold, bacteria cannot become infected with bacteriophages. If populations of bacteria grow beyond this point and try to dominate, virus infection kicks in and reduces population size until their numbers drop below the threshold again. This phenomenon has given rise to the concept of ‘killing the winning population’, which prevents overgrowth and thus preserves diversity in an ecosystem.
Biological weapon of nature: Virus
At this point, let’s take a look at the struggle between us and the animal viruses that we constantly come across. Animals that have learned to coexist with their ‘own’ viruses, such as bats, can use these viruses as a biological weapon to defend their niche. Humans faced these biological weapons when they invaded ecological niches inhabited by wild animals. We have experienced this situation over and over again. Consider the case of the Nipah virus. While clearing the forests of the Malay archipelago for the cultivation of palm trees, humans restricted the niches and food of the animals living in this niche. Fruit bats were under pressure from the dwindling food supply. At the same time, agronomists advised Malayan pig farmers to expand their agricultural activities by growing fruit trees (for example, mango trees) on pig farms. This attracted fruit bats that had lost their nests, ate cultivated fruit and contaminated it with bat viruses. Contaminated fruit was eaten by pigs, after which the virus was transmitted to pig farmers and slaughterhouse workers.
If we get too close to wild animals, we must consider the possibility that we will be exposed to their viruses. Animals may not show any clinical signs of viral infection as they have learned to live with their ‘own’ virus, but because the new host is naive to the new virus, the same virus can cause serious illness in the new host. This also applies, for example, to the Herpes B virus, which is harmless in monkeys but quite deadly in humans.
Just like bacteria, when the overgrowing human population invades wild habitats, viruses in these environments come face to face with humans. In fact, interspecies viral infections are rare because they require a suitable match of two compatible genetic environments. In particular, the more distantly related the species, the lower the probability of viral infection between species. This is why the virus is transmitted to humans not from animals such as reptiles, amphibians and fish but from warm-blooded animals such as mammals and birds. The virus is found in both domesticated animals and wild animals. We have been exposed to viruses from domesticated animals for several thousand years. We have had time to develop immunity to these viruses. However, this is not the case for wild animal viruses.
Did humans win or lose?
Live food markets offering wild animals represent risk areas where viral spread can occur to infect humans. This scenario took place at the outbreak of the SARS pandemic. In wet markets, bats infected palm civets, and then humans became infected. Although the origin of the SARS-CoV-2 virus is still unclear, it is significant that the COVID-19 pandemic originated in a livestock market in Wuhan. It is definitely time to regulate livestock markets where viral outbreaks may occur in the future.
The human population, now reaching 7.8 billion, is an ideal target for new viruses. Densely populated megacities are connected by travel and trade networks. Together with our domesticated animals, we are the “winning population” on earth. We created a burden that nature cannot bear. As a result, nature has taken the virus as an ally against humans, who destroy nature hostilely. Unless we read the Covid-19 pandemic correctly, it is impossible that we will survive against nature. Let’s finish by asking the question again: who is the enemy, and who is the ally in the triangle of humans, nature and viruses?
Reference:
Brüssow, H. (2020). On the role of viruses in nature and what this means for the COVID‐19 pandemic. Microbial Biotechnology.