Extensive research has shown that the novel coronavirus disease (COVID-19), which has affected millions of people around the world, emerged naturally despite various conspiracy theories. 

"There's no reason to believe this was made in a lab," Dr. Robert Shafer, a professor of infectious diseases at the Stanford University School of Medicine in the U.S., told ABC News.

"There are many strains in nature that could cause this type of outbreak," he added, according to a report on April 18 titled "Scientists have strong evidence coronavirus originated naturally."

Dr. Robert Garry, a professor at the Tulane University School of Medicine in the U.S., also refuted the theory that the virus was engineered as a biological weapon.

Dr. Garry told ABC News that a special mutation is thought to have made this coronavirus so contagious. If scientists had tinkered with the virus in the lab, that mutation would have changed or completely disappeared, he said.

The number of COVID-19 cases in the U.S. topped 800,000 on April 21 with deaths surpassing 43,000, according to the Center for Systems Science and Engineering at Johns Hopkins University that tracks reported cases in real time.

Copyedited by Sudeshna Sarkar

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