Relatives of the virus that causes COVID-19 pandemic have been in bats for decades

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By Joseph Giambrone, Auburn University professor emeritus

Close relatives of the SARS-CoV-2 have likely circulated in bats for decades before it was transmitted into humans, causing the worst pandemic in 100 years. A paper coauthored by Todd Castoe at the University of Texas-Arlington and published in the journal, Nature Microbiology, found no evidence that the virus was either manufactured or accidently released from a lab in Wuhan, China, as some have speculated. Sequencing of the entire viral genome of the SARS-CoV-2 virus and other coronaviruses isolated from bats over the past decades has shown they are similar and have been circulating and ready to infect humans for many years.

From the 1960s to 1970s, these coronaviruses were circulating undetected in bats and were ready to infect humans at any point. Scientists still don’t actually know when the novel coronavirus spread to humans, but studies have shown that bats were the reservoir for the virus. Researchers have speculated that the viruses from bats, sold in live animal markets, may have come from bats and spilled over in dogs, snakes, bats or pangolins that resemble armadillos. Using the sequences of the viral RNA of the coronaviruses isolated from these mammals showed they were 94 percent related to the SARS-CoV-2 virus isolated from bats. Using the current pandemic virus and the calculated mutation rate of the virus, the University of Texas-Arlington researchers have developed a molecular clock, which has determined that the virus may have emerged as early as the 1940s.

Their theory is that there was a lack of opportunity for the bat virus to be transmitted into humans during that time frame. They believe the evolution of the virus was a natural event. If it were intentionally engineered as a biological weapon, then the backbone of the virus would have had to be changed, which it was not. The early origin of the virus in the 1940s also makes it unlikely that the virus was synthesized or recently escaped from the Wuhan, China, lab.

Researchers from many labs across the globe have shown that mutations using genetic recombination of the viral RNA in nature are common. This long-ago divergence from the viruses in bats showed that there may be other viruses similar to the SARS-CoV-2 that are in bats that are waiting to infect humans. Scientists have known there are coronaviruses that bats harbor that can infect humans, including SARS and MERS, two of the viruses that have caused pandemics in humans over the past 20 years.

The University of Texas-Arlington study also suggested that, because these viruses are constantly mutating, it will be difficult to identify them until they cause disease in humans. This underscores the need for constant surveillance of viruses in bats in real-time. It is yet another sign that humans and bats need to be socially distanced. In many countries, humans hunt bats for food, and bats are often sold in live animal markets with other mammals, snakes, birds, etc.; this was believed to be the case in the Wuhan, China, fish market, where the virus may have originated.

Live animal markets need to be either shut down, selling of wild caught animals prevented and/or animals continually tested for viruses, as is done in many other markets in other parts of the world. Live animal markets in China have often been a source of human influenza viruses, which have been isolated from wild-caught or domestic-reared waterfowl or chickens reared in backyard or commercial operations.

About Joseph Giambrone:

Joseph Giambrone is a professor emeritus in Auburn University’s Department of Poultry Science with a joint appointment in the Department of Pathobiology in the College of Veterinary Medicine. During his graduate research career at the University of Delaware, he was part of a research group that developed the first vaccine against an antigenic variant of an avian coronavirus. During a sabbatical leave during his tenure at Auburn, he was part of a research group in Australia that sequenced the entire genome of antigenic variant of a coronavirus of chickens. During his 42-year research career as a molecular virologist, immunologist and epidemiologist, he has made critical advancements in understanding the ecology of viral pathogens, led efforts to improve detection and surveillance of viral diseases and developed new and effective vaccines and vaccine strategies to protect commercially reared chickens as well as pathogens, such as avian influenza viruses, which have spilled over into human populations. His research has had a profound impact on practices used today to reduce the incidence and severity of viral diseases of commercially reared poultry as well in human populations.

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