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One possibility is that this “flu” was actually a coronavirus pandemic. Specifically, four strains of coronavirus are responsible for about 20 to 30 percent of colds today, with far more death in the past. Epidemiologists believe that all four coronaviruses have been circulating among humans for the past few centuries. When they were just emerging, they probably caused major pandemics.
The parallel with our current crisis is that a better understanding of these other coronaviruses could be vital for a more effective response to covid-19. Ideas about the origins, spread, and characteristics of common coronavirus colds can provide key clues to what to expect in the months and years ahead. Understanding these relatively harmless coronavirus strains could also help us avoid the next pandemic, New Scientist writes.
Coronaviruses are a large family of viruses that primarily cause disease in livestock, and until recently have not caught the attention of virologists.
“Coronavirus was observed in humans in the 1960s, but the two strains detected only caused a common cold and did not pay much attention,” said pediatrician and epidemiologist Frank Esper of the Cleveland Clinic in Ohio.
The appearance of SARS
However, in 2002, a new, more serious strain of coronavirus, SARS (Severe Acute Respiratory Syndrome), began to spread worldwide, and was successfully contained the following year. The SARS-CoV-1 virus affected 26 countries and infected 8,000 people. She died every tenth. The high death rate from SARS has alarmed epidemiologists, and the coronavirus has come to the fore by experts from around the world.
A related virus has been found in bats, animals that manage to live with the coronavirus without contracting it. It is possible that the SARS epidemic occurred when bats infected the civet, after which SARS spread to humans.
Coronaviruses have proteins on their surface, which act as a key that opens the door for different cells to enter different host species. These proteins can be shaped and altered by genetic mutations or by the exchange of genetic material, thus opening new doors. Therefore, virologists searched for new coronavirus strains by tracing them in humans and wildlife to understand exactly what triggers protein modifications.
Marko Đoković
Coronavirus NL63
Microbiologist Lia van der Hoek of the University of Amsterdam, who has been honing her technology to detect unknown strains of the virus for some time, found another coronavirus strain, HCoV-NL63, in a 7-month-old baby with bronchiolitis.
– I came across the NL63 by chance, before I discovered SARS. Van der Hoek said. Other studies have shown that NL63 is a widespread occurrence and that this strain of coronavirus has infected between 1 and 9 percent of people with inflammation of the airways worldwide. NL63 causes fever, cough, sore throat, bronchitis, and pneumonia.
NL63 relatives were later found in pigs, cats, and bats. In 2012, experts discovered, through genetic comparisons of NL63 in humans and bats, that they had a common ancestor that lived 500 to 800 years ago. This means that NL63 crossed humans sometime between the 13th and 15th centuries. At the time, a pandemic was likely, according to virologist Ralph Baric of the University of North Carolina.
Like SARS-CoV-2, a coronavirus that causes covid-19, the native NL63 was somewhat fatal. Both viruses bind to the same cellular receptor.
– This long-standing pandemic looked like the flu but caused more severe symptoms in the elderly. Baric said.
Here again, the Russian flu enters history.
After the SARS epidemic, there was renewed interest in two apparently unexplained cold-causing coronaviruses that were discovered in the 1960s: HCoV-229E and HCoV-OC43.
By comparing these viruses with strains found in other animals, experts have concluded that OC43 must have come from cattle or pigs and transmitted to humans around 1890. Does the year sound familiar to you?
And it’s not just the 1890s that is the only factor linking OC43 to the Russian flu. Many people with Russian flu have severe symptoms that affect their central nervous system, and OC43 is known to infect nervous tissue. If OC43 is to blame for the 1889/90 pandemic, it has apparently slowly mutated into an increasingly dangerous virus in the past 130 years. The pandemic has likely lasted for several years, such as several severe flu seasons, and then OC43 has turned into a common cold.
What about the 229E? After isolation in the mid-1960s, experiments showed that half of the 229E-infected volunteers contracted colds after two to five days. Genetic comparisons of 229E and related animal viruses indicate that it went from African bats to camels and then to humans in the late 18th century. Like the MERS-causing coronavirus, it likely caused a deadly pandemic because humans had no immunity to that strain of coronavirus.
Millions of dead pigs
The idea that coronaviruses that caused the common cold were more deadly at first is supported by recent animal studies. In 2016, for example, a coronavirus caught a scientist who had just passed from a bat to a pig. In just a few months, 25,000 piglets died in China from the virus. And in 1977, the coronavirus caused a disease in pigs in Europe, which later spread to China and then to the United States, killing some 8 million pigs.
In 2005, a 71-year-old patient with pneumonia discovered a fourth strain of coronavirus that caused a common cold in a Hong Kong hospital. HCoV-HKU1 causes respiratory disease and subsequently became widespread worldwide. It appears to have changed from rodent to human. Although HKU1 is not as interesting to virologists as it does not cause more severe symptoms, it has been found to be more difficult to hit in older patients.
Tanjug / AP
All four coronaviruses have one similarity
The four coronaviruses that cause the common cold have an interesting characteristic: they vary.
– NL63 appears at higher levels in some years and at lower levels in some. In addition, between 2000 and 2010, NL63 and OC43 infections were reported more frequently in children than 229E and HKU1 infections. They are competing with each other. van der Hoek said.
Some epidemiologists believe the reason is that the immune system provides protection for a particular strain for a few years and then relaxes. But the reason could be more grim. A trial in 1990 found that subjects voluntarily infected with 229E were again susceptible to the same infection one year later. But then, they had no symptoms, they were only contagious, that is, they spread the virus more.
Studies of coronavirus causing colds have also yielded some encouraging results. The coronavirus family tree consists of four subgroups, two of which are human. NL63 and 229E, along with feline and canine coronaviruses, are in a group called alpha. OC43 and HKU1 belong to the beta group, which also includes viruses that cause MERS, SARS, and covid-19. Experts have noted that antibodies to a single virus can be effective in fighting a related virus in the same group.
– We should definitely investigate if people already had any immunity to covid-19 if they had OC43 or HKU1 infection. “ van der Hoek said, adding that there could be a reverse or negative scenario.
“If you are older and immune to some coronaviruses, your body is likely to overreact to a new strain,” he explained.
In the long term, virologists cannot predict what will happen to covid-19 at the moment. But there is a good chance that for a few more years it will cause severe symptoms in the elderly and those with other health problems, and then slowly turn into a common cold.
ALL ABOUT KORONAVIRUS READ HERE.
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