In 1965, researchers discovered an unpleasant respiratory tract infection called 229E. Today we know her as a common cold, but this is the first of the detected coronaviruses. Sometimes this “common cold” causes serious complications. This is one of the main challenges in the fight against coronaviruses.
In 2016, a 45-year-old school teacher was admitted to the emergency department of Athena Gigeya Hospital. A non-smoking woman who had never complained about health before had unusual symptoms – a temperature under forty, a dry cough and a severe headache. An ambulance doctor examined her and noted wheezing in the lower part of the left lung. The pathology was confirmed by an x-ray of the chest.
Believing that they are dealing with bacterial pneumonia, the doctors prescribed antibiotics to the woman. But in the next two days her condition worsened, and laboratory analysis of pneumonia was not found. When her breathing began to be interrupted, she was given oxygen and a new set of drugs. At the same time, the patient was tested for a wide range of possible pathogens, including various strains of influenza, legionella, whooping cough and other serious respiratory diseases, including severe acute respiratory syndrome (SARS) and the Middle East respiratory syndrome (BRS / MERS) – but did not find anything.
In fact, only one analysis turned out to be positive. It was so amazing that the doctors checked everything again. Everything was confirmed: the patient showed a familiar, but mysterious infection called 229E – the first of the detected coronaviruses.
Researchers in the early 1960s who discovered the 229E would be struck by the severity of the condition of the school teacher. They were actually looking for a virus that causes a cold. By the middle of the 20th century, methods appeared for isolating individual viruses, but they did not always work: for example, approximately 35% of patients with colds found viruses that could not be identified.
In 1965, a researcher at the University of Chicago, Dorothy Hamre, accepted the challenge and decided to close this blind spot. Studying tissue cultures of students with colds, she discovered a new type of virus, called 229E.
At the same time, a group of English researchers led by Dr. David Tyrrell studied a runny nose. They also isolated a new type of virus in tissue culture, it seemed to them. When Tyrrell’s team examined it under an electron microscope, they found that it resembles a virus isolated in the 1930s from chickens with bronchitis. This was coronavirus – the first one about which it is known for certain that it infected a person.
“Animals have always had these viruses,” explains Dr. Ken McIntosh of Harvard Medical School. – Here, for example, the virus of infectious avian bronchitis. It has long been known in the poultry industry, and there are vaccines for it. ”
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This early exploration is a kind of time machine. Today, biological research adheres to strict safety rules and isolation procedures, but half a century ago, these issues were easier to address. Here is what the then newspaper article told about Tyrrell’s findings: “Scientists placed samples of the medium in the nasal cavity of 113 volunteers. Only one caught a cold. That was enough. ” So his team determined the absence of the isolated virus in the cultures where it was grown.
During the discoveries of Hamre and Tyrrell, Dr. Mackintosh was on the team at the National Institute of Health, which also studied the causes of the common cold. (“Completely independent,” he adds, since no studies have been published so far). Dr. Mackintosh’s team discovered the so-called OC43, another common human coronavirus that still causes respiratory infections. In 1968, the term “coronavirus” appeared – because under an electron microscope its surface resembles the outer layers of the solar atmosphere, the corona.
At that time, the discovery of new coronaviruses like 229E and OC43 attracted intense interest from the press. One article recklessly proclaimed that science “tripled its chance to overcome the common cold.” However, the Macintosh recalls that the scientific community did not pay due attention to the study of coronaviruses until the appearance of SARS in 2003. Since 229E and OC43 caused relatively mild illnesses, doctors treated them like a common cold: antipyretic, expectorant and hot chicken stock.
Then in 2003, an outbreak of SARS broke out. It started with coronavirus in China and eventually infected 29 countries. Although the virus ultimately infected only 8,096 people, they attributed 774 deaths to it – such an amazingly high mortality rate made researchers look at it in a new way.
“When SARS appeared, the world of coronaviruses suddenly changed – it has become much wider, and technical details have been added,” says Dr. Mackintosh.
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Since then, two more coronaviruses have been discovered that also cause colds – NL63 and HKU1. And only in 2012 – almost 50 years after its discovery – the complete 229E genome was finally sequenced. In the meantime, cases have been reported where 229E caused severe respiratory symptoms in immunocompromised patients, although most healthy people get a cold.
Despite a thorough study of coronaviruses after an SARS outbreak, it is not yet clear why three of them – SARS-CoV-1, MERS-CoV and SARS-CoV-2 (the source of the COVID-19 pandemic) – cause more severe symptoms and lead to more high mortality, while the other four known human coronaviruses are much weaker.
However, they still have one thing in common: bats. All known coronaviruses that infect humans appear to come from bats. Then the viruses were transmitted to another animal (the favorable environment for them was game markets and open-air food markets), and in the end they reached a human being. So, OC43, apparently, has been circulating since the 18th century, and has been transmitted to humans from livestock. MERS-CoV was transmitted to humans from camels. Intermediate animals are also suspected of transmitting other coronaviruses up to SARS-CoV-2 to humans.
The Greek teacher eventually recovered – fortunately, mechanical ventilation was not needed. A lung scan two years after treatment showed that they recovered and fully recovered. Nevertheless, such serious complications of the “common cold” are one of the main difficulties in the fight against coronaviruses: they cause a range of symptoms of varying severity.
“If you look at the spread of disease during the current outbreak, right now,” says Dr. Wayne Marasco, a researcher at the SARS, BRS and COVID-19 specialist at the Boston Cancer Institute in Boston, “then some people have the disease completely asymptomatic, while others die. ”
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Dr. Macintosh suspects that coronaviruses will continue to confuse researchers. Firstly, they are large and complex, and secondly, they can be relatively easily changed at the genetic level. He notes that even these viruses are relatively easy to disassemble and assemble in the same cell. It is precisely such mutations that, apparently, caused both SARS and today’s pandemic.
“Coronaviruses have the largest RNA genome among all animal viruses,” says Dr. MacIntosh. “So they have a lot of secrets.”
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Forbes (USA)
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