Health

More theories about the origin of Covid-19


Some scientists believe that the corona virus, the ancestor of nCoV, is a sub-lineage, left over from the flu strain that spread in Russia in 1889.

In May 1889, many people living in Bukhara, Russia, fell ill and died unexpectedly. They are believed to have contracted a respiratory virus called Russian flu. It swept the world, overwhelmed hospitals, killed many elderly people.

Schools and factories were forced to close because too many students and workers contracted the virus. Some patients have strange symptoms: loss of smell and taste. Some people who recovered from the illness reported persistent exhaustion.

The Russian flu ended a few years later, having caused at least three waves of infections.

Epidemiological patterns and typical symptoms make scientists ask the question “Is Russian flu a pathogen caused by corona virus?”. What clues does it give the community about when and how the Covid-19 pandemic will end.

If a coronavirus causes the Russian flu strain, many believe the pathogen is still circulating somewhere. Its descendants spread worldwide as one of four strains of coronavirus that cause the common cold, which is not dangerous. As such, it is different from the pandemic influenza virus that spreads for several years, then is replaced by a new strain, leading to a new pandemic. If that’s what happened with the Russian flu, it could bode well for the future.

Another conjecture is that the virus behaves like seasonal flu, with immunity weakening over time. This means that the community will have to get a Covid-19 vaccine every year.

Medical historian Frank Snowden, of Yale University, USA, said that experts have very little hard data on the Russian flu epidemic. But molecular biologists can take the old virus from the lung tissue of Russian flu victims, find out what kind of virus it is. Some researchers are hunting for these samples, which are often kept in vials of solution at museums and medical schools.

Rapid Covid-19 test in Washington, USA, January 2022. Photo: NY Times

Tom Ewing, one of the few historians who has studied the Russian flu, says it has a significant resemblance to Covid-19: Countries have had to close schools and workplaces because too many people were sick. , doctors are overloaded, many consecutive infections. Dr. Ewing speculates that the Russian flu may have originated from a corona virus.

Professor Scott Podolsky, department of global health at Harvard Medical School and professor Arnold Monto, University of Michigan, USA, also agree with this hypothesis.

“We have long wondered where the corona virus came from? Has there been a pandemic from this virus in the past?”, Professor Monto said.

Citing a report published in 2005, biologist Harald Bruessow, editor of the journal Microbial Technology, mentions a still circulating corona virus (name OC43) that originated in cows, infecting humans in 1890 , close to the time of the Russian flu outbreak.

Three other coronaviruses of lesser virulence also exist today. Experts believe that one of them (or OC43) is a strain left over from the Russian flu epidemic. Dr. Bruessow and colleagues found that a number of patients during the 1889 outbreak complained of persistent loss of taste, smell, and Covid-19-like symptoms.

Some medical historians speculated that chronic fatigue in the 19th century was a sequel to the Russian flu. Like Covid-19, Russian flu kills older people instead of children. Examining records from the Connecticut State Board of Health, Dr. Ewing found a similar epidemiological pattern. But the records do not answer the question of whether the coronavirus caused the Russian flu.

At this point, the idea that the Russian flu could be caused by a coronavirus is still speculative, said Peter Palese, an influenza researcher and professor of medicine at the Icahn School of Medicine at Mount Sinai. New York, said. He said “there is no clear link between the Russian flu pandemic and a coronavirus” and ruled out influenza.

Past pandemics may offer clues as to when Covid-19 will end. According to Alexander Navarro, a historian at the University of Michigan, when the Russian flu epidemic waned, “people quickly returned to normal life,” similar to the 1918 Spanish flu. Stories about it in the press less and less.

“I think Covid-19 is also going in this direction,” he said.

Previously, experts hypothesized that Covid-19 originated in bats, then spread through an intermediate host and then transmitted to humans. However, the World Health Organization (WHO) and some scientists do not rule out the possibility that the virus leaked from a laboratory in China.

Quite a few pandemics over the past century have been caused by respiratory viruses. Exceptions are Zika and chikungunya viruses (mosquito-borne viruses) or HIV viruses (sexual and blood-borne viruses).

The most prominent epidemic in history was the bubonic plague, which ushered in a period of crisis that killed many Europeans between 1347 and 1357. The plague returned to the continent for many centuries. But the plague does not offer many lessons for today’s pandemic. For a long time, experts tried to find the factor that stopped it from spreading, but there was no answer.

So they turned to the study of influenza viruses and respiratory pandemics in general. This process is still fraught with difficulties. “We only have 104 years and four different pandemics to make predictions about,” said David Morens, senior adviser at the National Institute of Allergy and Infectious Diseases.

189,000x magnification image of the H1N1 flu strain.  Photo: NY Times

189,000x magnification image of the H1N1 influenza virus strain. Photo: NY Times

The first flu pandemic began in 1918, waning after three waves of infection. The virus then known as H1N1 remained circulating in a low virulence form until 1957, then disappeared. Next, H2N2 emerged. By 1968, the H3N2 strain appeared. In 1977, H1N1 made a comeback after two decades. It and the H3N2 strain of influenza circulated simultaneously since then.

“Before 1977, the world never had two types of flu circulating at the same time,” Dr. Monto said.

In 2009, H1N1 re-entered the community, but existed in a genetically distinct version, known as “swine flu”, causing a pandemic.

During that time, scientists could not explain why previous strains of flu disappeared forever. But they have successfully developed a useful vaccine against the flu, which is given every year.

Thuc Linh (Follow NY Times)

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