Contents
Coronaviruses are a huge family of viruses that includes dozens of species. They usually affect animals, but sometimes the viruses mutate and can cause disease in humans as well. For the first time, one of the coronaviruses was discovered in humans in the middle of the 20th century.
Many coronaviruses are constantly circulating in the environment and do not cause disease more than the common cold. About 80% of people have antibodies to certain types of coronaviruses. It is likely that many people have already suffered a mild illness, mistaking it for a common cold.1.
Some types of coronaviruses cause more severe illness, and they deserve special attention. So, the first outbreak of acute respiratory syndrome occurred in 2002 in China – then about 8 thousand people fell ill and the disease did not spread so much. Then there was an outbreak of Middle East respiratory syndrome in 2012 in Saudi Arabia. Its difference was that bats infected camels with the coronavirus, and they, in turn, became a reservoir of infection for humans. New cases of these viruses still occur in the Middle East2.
“Such outbreaks of diseases caused specifically by coronaviruses have been happening periodically for a long time, and the mortality rate from some of them was higher than from the last epidemic,” says biotechnologist Denis Yudchits.
This is the first time that a new strain of COVID-19 coronavirus has caused such a large-scale epidemic that has swept many countries. The virus has adapted to the human body, and you can become infected even during the incubation period, when there are still no visible symptoms. An infected person can spread the virus for about 10 days without feeling sick at all.3.
The main versions of the appearance of COVID-19
There are many hypotheses about where the coronavirus came from in China, from strictly scientific to conspiracy theories. Let’s consider some of them.
Seafood
Previously, it was assumed that the first person contracted the coronavirus through seafood from a food market in the city of Wuhan. However, studies have shown that another product from the same counters is to blame, since no similar virus genomes were found in any seafood.4.
Bats are the source of the disease
The official and most likely version of the emergence of coronavirus in China is a virus that mutated in the natural environment, the source of which was infected bats. It was they who discovered the hybrid COVID-19.
The outbreak began in the city of Wuhan at a market that is also called “wet” because of the active pouring of water on all the stalls to wash away contamination from the many curios sold there. In the market, you can buy various seafood, as well as try bat soup or eat a snake. The Chinese love this type of food and eat a lot with little or no heat at all. Thus, the virus did not die and, having entered the human body, mutated. The market was closed on January 1, 2020, after finding symptoms among sellers and buyers.
Scientists carefully analyzed the genome of the virus and found that the similarity between the bat coronavirus and COVID-19 is incomplete. One fragment of the genome was different, which means that another animal carrier was involved. Such a fragment was found in poisonous snakes, which are also sold in abundance in the Wuhan market, and are often eaten raw.
Probably, the snakes hunted bats, became infected with the virus, and only then passed it on to humans. However, experts in virology at the Institute of Zoology in Beijing emphasize that the similarity of genetic codes is not sufficient reason to confidently call snakes an intermediate link in this chain.5.
In addition, the possible fallacy of the version is indicated by the fact that the virus had to adapt to both cold-blooded and warm-blooded animals. This is unlikely, because during previous epidemics of such infections, viruses were transmitted to humans exclusively from mammals – camels, civets.
Infected bananas
Many stopped eating bananas, considering them a source of infection. It is believed that infected poisonous snakes climb on bunches of bananas and eat them – after that, all the fruits become dangerous. Scientists refute this version, and consider such a route of infection impossible.
For the first time, the fact that the coronavirus is artificial and escaped from secret laboratories was talked about almost immediately. For example, scientists at the Broad Institute at the Massachusetts Institute of Technology and Harvard University, who specialize in genetic engineering, have repeatedly stated the need to investigate the possibility of leakage from the laboratory. 18 scientists even published a May 14, 2021 letter in the journal Science calling for deeper research into the origin of the virus, taking into account theories of both natural origin and laboratory side effects.6.
The researchers offered near-uniform conclusions that multiple conclusions could be drawn from the available scientific evidence, and China did not provide any information in the early days of the pandemic. In recent months, there has been no new evidence of laboratory origin of the virus, and studies conducted in the Wuhan market in China have not confirmed this theory.
Hypotheses in action
A number of theories about how the virus might have appeared have been dismissed. Most of the rest fall into three possible scenarios:
- The virus evolved naturally before passing to humans from an infected animal.
- The virus evolved naturally, but a lab worker became infected from a sample and accidentally “smuggled” it into the community.
- Laboratory scientists manipulated virus samples and accidentally or intentionally released the pathogen.
What makes the origin of the virus so debatable is that its various mutations and fragments are difficult to explain. While most virologists have said that the coronavirus likely evolved in nature, they agreed that it is prudent to explore the possibility that it came from a laboratory. At the heart of these suspicions is the Wuhan Institute of Virology, a research center founded in the 1950s that was the first in China to receive the highest level of biosecurity approval. The Institute’s laboratory is Biosafety Level 4 (known as BSL-4, the highest level). This means it is equipped to study the world’s most dangerous infectious agents and toxins, which require the strictest biological containment. It was this designation and the location of the laboratory in the city where the outbreak was first reported that made the institute one of the first suspects.
However, scientists say that while a lab leak is likely, that doesn’t necessarily mean it’s the most likely explanation. It is more likely that the virus was transmitted to humans from an animal such as a bat. The experience of conducting field epidemiological studies of avian influenza in Vietnam from 2008 to 2016 showed how close contact with wildlife is, for example, in “wet markets” around the world, where meat, seafood and live animals are sold in street stalls for human consumption, can create easy opportunities for pathogens to enter the human population.
The origin of animals is considered as the main version. The first case of Covid-19 infection has been traced to the Huanan Seafood Market in Wuhan, leading to speculation that this may have been the place where the virus jumped from animals to humans. But Chinese researchers have since found that several of the city’s earliest known cases of Covid-19 were not linked to a market, meaning the virus may have already been spreading in the community.
A joint investigation by the World Health Organization and China this year focused on the possibility of zoonotic or animal origin. The team’s report, published in March, indicated that the virus likely originated in bats and jumped to an intermediate animal before it spread to humans.
The team also dismissed the theory that the virus leaked from the Wuhan Institute, describing the scenario as “highly unlikely.” But the WHO investigation has been heavily criticized for not sufficiently testing all plausible hypotheses. And the credibility of the results has been called into question because the investigation depended on China’s cooperation, and the Chinese government didn’t give the researchers access to the full records and raw data.
Calls for deeper investigation of both the natural origin theory and the lab leak hypothesis have been supported, at least in part, by the growing amount of circumstantial evidence unearthed over the past year by a group of anonymous internet sleuths. Last year, a member of an amateur investigative team that calls itself DRASTIC (short for Decentralized Radical Autonomous Search Team Investigating Covid-19) sifted through online records and found a 2013 dissertation from a graduate student at Kunming Medical University in China that described six mine workers in the province. Yunnan who fell ill with severe pneumonia caused by a coronavirus similar to SARS. In the end, three miners died, but little more is known about the situation. In a study published in November by scientists at the Wuhan Institute, serum samples from four miners were tested and showed no trace of SARS-CoV-2, the virus that causes Covid-19.
What are the conclusions?
All evidence for the origin of the virus to date is circumstantial and is consistent with both laboratory and natural origin. And it may be years or even decades before scientists clarify this topic. For example, the Ebola virus, discovered in 1976: it is believed that it spread to humans from bats or non-human primates, but scientists have not yet determined the origin from a specific animal host.
Sources of
- Romanov B.K. Coronavirus infection covid-2019 // Safety and risk of pharmacotherapy. 2020. №1. https://cyberleninka.ru/article/n/koronavirusnaya-infektsiya-covid-2019
- The Independent Panel for Pandemic Preparedness & Response COVID-19: Make it the Last Pandemic (Independent Panel, 2021). https://theindependentpanel.org/mainreport/
- Zemtsov Stepan Petrovich, Baburin Vyacheslav Leonidovich Coronavirus in the regions of Russia: features and consequences of the spread // Public Service. 2020. No. 2 (124). https://cyberleninka.ru/article/n/koronavirus-v-regionah-rossii-osobennosti-i-posledstviya-rasprostraneniya
- Shchelkanov Mikhail Yuryevich, Popova Anna Yuryevna, Dedkov Vladimir Georgievich, Akimkin Vasily Gennadievich, Maleev Victor Vasilyevich HISTORY OF STUDY AND MODERN CLASSIFICATION OF CORONAVIRUSES (NIDOVIRALES: CORONAVIRIDAE) // Infection and Immunity. 2020. №2. https://cyberleninka.ru/article/n/istoriya-izucheniya-i-sovremennaya-klassifikatsiya-koronavirusov-nidovirales-coronaviridae
- Coronavirus Disease Pandemic (COVID-19): Challenges and a Global Perspective. Pathogens 2020, 9(7), 519; https://doi.org/10.3390/pathogens9070519
- Investigate the origins of COVID-19 BY Jesse D. Bloom, Yujia Alina Chan, RALPH S. BARIC, PAMELA J. BJORKMAN, SARAH COBEY, BENJAMIN E. DEVERMAN, DAVID N. FISMAN, RAVINDRA GUPTA, AKIKO IWASAKI, MARC LIPSITCH, RUSLAN MEDZHITOV, RICHARD A. NEHER, RASMUS NIELSEN, NICK PATTERSON, TIM STEARNS, ERIK VAN NIMWEGEN, MICHAEL WOROBEY, DAVID A. RELMAN. SCIENCE14 MAY 2021 :