Two new cases of COVID-19, the disease caused by the novel coronavirus, have been reported in Aiken County, bringing the countywide total to six as of Friday afternoon.

Cases have been reported in zip codes 29803, 29841 and 29842, according to a new map available on the S.C. Department of Health and Environmental Control website. Zip code 29803 comprises southern Aiken and areas around New Ellenton and the Savannah River Site; 29841 and 29842 comprise the greater North Augusta region.

Nearly 600 COVID-19 cases have so far been reported in South Carolina. Thirty-nine counties are affected. And DHEC's public health lab has run 2,408 COVID-19 tests as of Friday afternoon.

Gov. Henry McMaster during a public briefing announced all visitors coming to South Carolina from virus hotspots – New York, New Jersey, Connecticut and New Orleans – must quarantine for 14 days.

"The one thing I would like to announce is I've just issued another executive order. There is a mandatory quarantine," McMaster said. "We know that there are hotspots around the country. They've been identified, some very clearly, others are being identified now."

The Republican governor repeated the message on Twitter.

The finer points of enforcement aren't immediately clear, though McMaster said violators would face jail time or a $1,000 fine.

"We hope that our visitors will be as responsible as the people of South Carolina have been in following the recommendations and the requirements," the governor explained during his briefing. "This is a requirement that has the force of law, and that's why it carries a criminal penalty."

Thirteen coronavirus-related deaths have been reported in South Carolina – four more compared to Thursday.

McMaster has voiced his opposition to a statewide "stay-at-home" order. He reiterated that position Friday, despite moves by Charleston and Columbia to do so, closing businesses like nail salons, gyms and barbershops. Earlier in the day, S.C. Attorney General Alan Wilson issued a non-legally-binding opinion that a governor's order during a state of emergency would preempt municipal ordinances, essentially saying only the governor – not cities or counties – could issue such measures.

Both Myrtle Beach and North Myrtle Beach have ordered most visitors to leave by the weekend and told all hotels, motels, private rental companies and campgrounds to stop taking new reservations until at least May 1. Existing reservations are to be canceled or rescheduled.

Also Friday, the newest member of South Carolina's congressional delegation, Charleston Democrat Joe Cunningham, said he had been diagnosed with the virus and had already been self-quarantining for more than a week.

Associated Press reports were used in this article.

Colin Demarest covers the Savannah River Site, the U.S. Department of Energy, the National Nuclear Security Administration and government in general. Follow him on Twitter: @demarest_colin