Dr. Anthony Fauci
Top infectious disease expert Dr. Anthony Fauci responds to accusations by Sen. Rand Paul (R-KY) as he testifies before the Senate Health, Education, Labor, and Pensions Committee on Capitol hill in Washington, D.C., U.S., July 20, 2021. J. Scott Applewhite/Pool via REUTERS

San Diego County public health officials reported 530 new COVID-19 cases Tuesday as a national trend continued upward due to the highly contagious Delta variant and infection rates among the unvaccinated

Local officials reported 439 new cases of COVID-19 Monday. Saturday — with 501 new cases reported — marked the first time the county had seen daily case levels of more than 500 since February.

With the new numbers, the total local COVID-19 cases rose to 288,224, while the death toll remained at 3,786.

The Delta variant of the coronavirus is the cause of more than 80% of new U.S. COVID-19 cases, but the authorized vaccines remain more than 90% effective in preventing hospitalizations and deaths, said top U.S. infectious disease expert Anthony Fauci during U.S. Senate hearing on Tuesday.

The hearing featured a pointed exchange with Republican U.S. Senator Rand Paul, in which he accused Fauci of lying about the National Institutes of Health providing funding for research at China’s Wuhan Institute of Virology.

The Senator from Kentucky, who has sparred with Fauci during several pandemic-related hearings, alleged that the research may have played a role in developing the novel coronavirus at the Wuhan Lab.

“If caught lying to Congress… the U.S. criminal code creates a felony and a five year penalty,” Paul said to Fauci during the hearing.

Fauci, who has been mostly calm and diplomatic in past responses, this time shot back: “Senator Paul, I have never lied before the Congress… (and) you do not know what you’re talking about.” The exchange featured raised voices and pointed fingers.

The origin of the novel coronavirus has become a heated partisan issue in the United States, with Republicans urging further inquiries into whether it was developed in a laboratory in Wuhan, China.

President Biden in late May called on aides to investigate the origins of the virus and to report back to him within 90 days. The more prevalent theory is that the virus originated in animals, possibly bats, and was passed on to humans.

Reuters contributed to this article.