WASHINGTON, May 5 (Xinhua) -- A U.S. researcher who had worked with a Wuhan virology lab told U.S. media in a recent interview that the start of the COVID-19 pandemic is "highly unlikely a lab accident."

"We worked together to develop very stringent safety protocols, and it's highly unlikely this was a lab accident," said Jonna Mazet, an epidemiologist at the University of California, Davis, who has worked with and trained researchers at the Wuhan Institute of Virology (WIV).

In an article published on Sunday by Business Insider, a leading news website in the United States, Mazet gave four reasons against the ungrounded assertion.

The first reason, she argued, is that "the lab's samples don't match the new coronavirus."

Mazet has worked with Shi Zhengli, a virologist at the WIT, through PREDICT, a pandemic early-warning program started by the U.S. Agency for International Development.

"I've spoken to her recently," Mazet said of Shi. "She is absolutely positive that she had never identified this virus prior to the outbreak happening."

Secondly, the WIV implements rigorous safety protocols that are "above reproach."

"In the field, they (researchers) wear extreme personal protective equipment, including multiple layers of gloves, eye protection, full body suits and masks," said Mazet.

After a series of disinfection procedures, researchers only use the deactivated, non-infectious samples, and the containers with viable virus are locked down in a special area, she added.

"Rather than a leak," Mazet said of the third reason, "the novel coronavirus is more likely the latest disease to have jumped from an animal to humans."

Mazet mentioned that the 2003 SARS outbreak, Ebola and the H1N1 "swine flu" pandemic are all caused by viruses originated in other species, which are known as zoonotic diseases.

Genetic research has all but confirmed that the virus causing COVID-19 originated in nature, she said, noting that a study published in February found that it shares 96 percent of its genetic code with coronaviruses circulating in bat populations.

As for the fourth reason, Mazed noted that everyday people are more likely to get infected than researchers who wear protection, which indicates that a leak from a lab is implausible.

Tourists, hunters and other people who rely on animals in some capacity for food or trade wander into wild habitats less protected and are therefore exposed to the live viruses circulating in the animals.

The frequency of cross-species infections "will increase as humans encroach further into wild habitats that house disease-carrying species we haven't interacted with before," added Mazet.