Robert Redfield, the former director of the Centers for Disease Control and Prevention (CDC), believes that the COVID-19 originated from a lab and not in a wet market where an initial cluster of cases was linked to.

Robert Redfield told CNN on Friday that it was his "opinion" that the coronavirus did not evolve naturally, New York Post reported.

"I'm of the point of view that I still think the most likely etiology of this pathology in Wuhan (in China) was from a laboratory - escaped," Redfield said.

Dr. Anthony Fauci then refuted Redfield's claims by reiterating that it was simply an opinion that the former CDC director has expressed.

The nation's top infectious disease expert noted that the COVID-19 was likely already spreading in China weeks before it was identified, according to another NY Post report.

And if that were the case, Fauci said the coronavirus clearly could have adapted itself to greater efficiency of transmissibility over that period of time, up to and at the time it was recognized. 

According to Robert Redfield, who oversaw the CDC at the peak of the deadly pandemic, it is not unusual for respiratory pathogens being studied in laboratories to infect a lab worker.

He added that the virus might have already started circulating in Wuhan as early as September 2019, earlier than its official timeline, Daily Mail reported.

As a virologist, who has spent his life in virology, Robert Redfield said it does not make "biological sense" to him that the COVID-19 came from a bat and then jumped to a human or intermediary species in a market.

He believes that a lab was already studying the coronavirus and that COVID-19 was exposed to human cell cultures.

Robert Redfield said that other people might not believe that, but "science will eventually figure it out."

RELATED ARTICLE: Growing Evidence Shows COVID-19 Leaked From Wuhan Lab, Contrary to China's Claims

Origin of COVID-19

The origin of COVID-19 remained mysterious as researchers continue to study the virus. Debates on where the virus came from continued, and it has already resulted in tensions between the U.S. and China.

U.S. investigators have been blocked from going to China to probe the virus' probable origin. China has refused entry of the investigators and insisted that the virus did not come from their country.

Members of the World Health Organization (WHO) expert team have already announced that the origin of the COVID-19 coming from a laboratory leak in China is "extremely unlikely," according to a USA Today report. However, one WHO scientist does not rule out the lab leak as the outbreak's possible source.

Professor John Watson, a former deputy chief medical officer who joined the WHO investigation team, said the virus was already spreading in other parts of the world, particularly northern Italy, as early as September and October.

He noted that China was by no means necessarily the place where the leap from animals to humans took place. Watson said that people should also look beyond the borders of China, Independent reported.

In Milan, a study by its National Cancer Institute showed that the contagious virus was already spreading in Italy in September 2019.

It revealed that 11.6 percent of 959 healthy volunteers who participated in a lung cancer screening trial between September 2019 and March 2020 had antibodies for the virus. However, Watson maintained that the narrative that COVID-19 came from a Wuhan lab remains on the table.

The United States has a total of 30.1 million COVID-19 cases with around 547,000 deaths. California is the state with the highest cases at 3.65 million, with 58,512 deaths.

READ MORE: Experts Suggest Novel Coronavirus Originated From Lab in Wuhan 

WATCH: Former CDC Chief Says He Thinks COVID Originated in Wuhan Lab - From Bloomberg Quicktake: Now