In early March 2020, the head of the World Health Organization declared the coronavirus epidemic a pandemic. Where the coronavirus originated in China is not entirely clear. The media publishes a huge number of possible causes, but the opinions of experts on the origin of the virus differ. The article selected the most thorough approaches to answering the question of why human infection became possible.
The COVID-19 outbreak is the 10th recorded pandemic, with Spanish flu, black plague and HIV among others.
Where did the coronavirus come from in China
At the beginning of the investigation into the emergence of the Chinese virus, it was assumed that the epidemic started from the food market in Wuhan. For some time, the main confirmed version of the appearance of coronavirus in humans was infection through seafood. After conducting a study, Chinese infectious disease specialists and doctors found that about half of the initially infected people visited the seafood market. However, neither the very first infected nor his family visited the fish market. It is obvious that the market is somehow connected with human infection. But how?
Infectious disease expert Wilt Jan Lipkin suggested that the primary origins of the disease should be sought before the animals hit the market, since infections on the market were most likely already secondary. Chinese researchers of the genome of the COVID-19 virus said that the genomes of samples from 12 countries are younger than the genome of the virus found on the market and are its modifications. This confirms that the coronavirus appeared in the seafood market, it remains to be seen how it got here.
By comparing different types of coronavirus, scientists are trying to find similar types in order to determine the cause of human infection. This is how the source of another coronavirus epidemic was previously identified: bats.
Regardless of the animal — the primary carrier of the virus, scientists named the cause of the outbreak of pneumonia in China:
- Population density. The virus is transmitted by airborne droplets, and with such crowding of people, the likelihood of infection is high.
- All kinds of animals are sold in the markets of China. They are in demand and eaten.
- The southern territories of China are located in a humid warm climate zone that favors the vital activity of infections.
It so happened that it was in China that all these factors contributed to the spread of the coronavirus.
Coronavirus is transmitted not only by airborne droplets. Other ways: air-dust, fecal-oral and contact.
There is another possible reason for the emergence of coronavirus in China. Zhao Lijian, a member of the Chinese Foreign Ministry, claims that the United States brought the infection to China as a biological weapon. He argues his words with the impossibility of learning about the spread of the virus in America and doubts the presence of infected people there. On the social network, Zhao Lijian asks America for an explanation and reveal the names of hospitals that treat the infected.
How did the transmission of a new virus from animals to humans begin?
US biologist Christian Andersen suggested that the transmission of the virus occurs in three ways: from animal to person, from person to person, and from a group of people to person.
From the rulings on the COVID-19 genome, it turned out that bats did contribute to human infection, but there must be another link. In this link, the virus had to mutate in such a way as to become infectious for humans. Humans currently lack immunity to the novel coronavirus.
Scientists have found the following: snakes may be the missing element of the mosaic. It was in snakes that the virus mutated, and not seafood became a possible reason for the virus's access to humans.
But how animals got infected: versions
Coronaviruses are a whole group of viruses that can infect both humans and animals. The difference is only in the form of the virus itself. For animals - one set of genes, for humans - another. But fundamentally, the structure of the coronavirus is the same. The genome of COVID-19 is in many ways similar to the genome of the virus that causes SARS, and the symptoms of the disease are similar to those of influenza and SARS.
Leading versions claim that the new coronavirus is a mutated relative of those coronaviruses that have previously infected animals. Only living organisms have already developed immunity to them. Infection of animals occurred according to the standard scheme: the body of the virus with the help of the crown “deceives” a healthy cell in order to get inside. And then he, at his own discretion, begins to change the structure and work of the cell.
Virus tracking not complete
So far, it is impossible to say with certainty exactly how the virus spread before it entered the human body. Understanding this will help in the development of vaccines and the fight against the epidemic. At the moment, it is known that the body of the coronavirus COVID-19 and the coronavirus found in bats are 95% identical. On this basis, it can be argued that the bat is a natural carrier of the infection.
Similar virus genes have been found in snakes and pangolins. Snakes eat bats in the wild, which may explain the mode of transmission. It remains unclear how the virus adapted from a cold-blooded reptile to a warm-blooded mammal.
As for pangolins, these are mammals that are in great demand in the market. They also have a coronavirus similar to the human one, but it is too early to declare the pangolin as an intermediate link.
The coronavirus in China could have appeared either through the evolution of the virus, or through the conscious actions of bioengineers. The infection is present in both humans and animals, and until scientists track the full path of infection from the source to humans, the correct conclusion cannot be drawn.