U.S. President Joe Biden's nominee to become surgeon general, Dr. Vivek Murthy, told The Washington Post Live that he thinks the United States has a "good shot" to get all kids in school by the fall.

Murthy, a physician who served as U.S. surgeon general from 2014 to 2017, said the nation must takes these steps: vaccinate staff; ensure schools have the resources to take precautionary measures including PPE and tests; and lower "background rates of infection," which he defines as rates of transmission in the community.

"When those rates are really high, it makes it harder to prevent infection from getting into the school," Murthy said. "So we've got to get that background infection rate down, and we've got to vaccinate teachers and other educators and staff in schools. As well as, when we do have the opportunity to vaccinate kids when the trial data comes through and shows that it is safe and effective, that we've got to start vaccinating children, too."

ABC News’ Anne Flaherty contributed to this report.

The United States’ first known cases of the South Africa variant of the novel coronavirus have been confirmed in two people in South Carolina, according to the South Carolina Department of Health and Environmental Control.

"There is no known travel history and no connection between these two cases," the department said in a statement Thursday.

Both cases are among adults, one who is from the Lowcountry region and another who is from the Pee Dee region, according to the department.

The U.S. Centers for Disease Control and Prevention said it's aware of the cases and it "recommends that people avoid travel at this time."

The so-called B1351 variant, first identified in South Africa, has been detected in more than 30 countries, according to the South Carolina Department of Health and Environmental Control.

"Experts agree that existing vaccines work to protect us from this variant, even if we don’t know precisely how effective they are," the department said. "At this time, there’s no evidence to suggest that the B.1.351 variant causes more severe illness."

During an interview Thursday on ABC's "Good Morning America," Dr. Anthony Fauci, chief medical adviser to U.S. President Joe Biden and the nation's leading infectious disease expert, said the South Africa variant "troubles" him.

Fauci said lab experiments show the neutralizing antibodies induced by existing COVID-19 vaccines are "diminished by multifold" when tested against the B1351 variant

"It's still within the range of what you would predict to be protective," he said, "but I take no great comfort in that."

However, scientists are already working on vaccines that will specifically target the South Africa variant, according to Fauci.

"May not be necessary," he said, "but if it is we'll already be on the road to be able to give people a boost that directs against the South African isolate."

In the span of two weeks, the United States' seven-day average of daily COVID-19 cases has declined by 34% -- the steepest non-holiday-related drop in cases the country has seen since the summer, according to ABC News’ analysis of data compiled by The COVID Tracking Project, a volunteer-run effort to track the U.S. outbreak.

California appears to have seen the most drastic drop of any U.S. state, as its seven-day average of daily cases has been nearly slashed in half over the last two weeks.

Despite continued positive signs in case and hospitalization trends, daily death numbers are still incredibly high.

Another 3,943 fatalities from COVID-19 were reported on Wednesday, according to data collected by Johns Hopkins University -- that is approximately one death recorded every 22 seconds.

ABC News’ Arielle Mitropoulos contributed to this report.

COVID-19 cases and deaths are surging across Africa as new, more contagious variants of the novel coronavirus spread to additional countries, the World Health Organization warned Thursday.

"The variant which was first detected in South Africa has spread quickly beyond Africa and so what’s keeping me awake at night right now is that it’s very likely circulating in a number of African countries," Dr. Matshidiso Moeti, the WHO's regional director for Africa, said in a statement.

Diagnosed COVID-19 infections increased by 50% in Africa between Dec. 29 and Jan. 25, when compared with the previous four weeks. Deaths from the disease rose two-fold in the same period, with over 15,000 concentrated in 10 mainly southern and northern African nations, according to the WHO.

Over the last week, more than 175,000 new cases and over 6,200 new deaths were reported across the continent. There was a small dip in cases in South Africa, but 22 countries continue to see their numbers surge, according to the WHO.

The B1351 variant, first identified in South Africa, is "predominant and powering record case numbers in South Africa and the sub-region," the WHO said. The strain has been detected in Botswana, Ghana, Kenya, the French Indian Ocean region of Mayotte, Zambia and at least 24 non-African nations, according to the WHO.

Meanwhile, another new, highly contagious variant called B117, which was initially detected in the United Kingdom, has been found in Gambia and Nigeria.

The WHO said it is working to track and tackle new strains of the deadly virus. The U.N. agency, along with the Africa Centers for Disease Control and Prevention, has helped set up a COVID-19 genomic sequencing laboratory network with labs in the Democratic Republic of the Congo, Gambia, Ghana, Kenya, Nigeria, Senegal, South Africa and Uganda.

"In addition to the new variants, COVID-19 fatigue, and the aftermath of year-end gatherings risk powering a perfect storm and driving up Africa’s second wave and overwhelming health facilities," Moeti said. "Africa is at a crossroads. We must stick to our guns and double down on the tactics we know work so well. That is mask wearing, handwashing and safe social distancing. Countless lives depend on it."

Forty people in Gambia who tested positive for COVID-19 over the past week have refused to self-isolate or have escaped treatment centers, according to the country's health ministry, which vowed to reveal the identities of those flouting public health regulations.

Officials are also aware of a "large number of travelers who recently arrived" in the small West African nation from countries considered COVID-19 hotspots and "have refused to abide to official protocols and/or report to the health authorities for the mandatory test upon arrival," said Modou Njai, director of health promotion and education at Gambia's Ministry of Health.

"The Ministry continues to treat these matters with utmost and grave concern and thus, the Ministry is hereby giving an order and ultimatum to all those concerned, that they are required to report themselves to the health authorities with immediate effect and failure of which will lead to serious consequences, including the publication of names and identifying information of all those at large," Njai said in a statement Tuesday.

"The Ministry would like to stress that this serious and ruthless misconduct will no longer be condoned under any circumstances," he added. "Anyone found not willing to cooperate with COVID-19 regulations will have their names and identifying information published on the media and thereafter, drastic measures will be taken against anyone that is non-compliant."

Gambia, home to some 2.3 million people, has confirmed 4,008 cases of COVID-19 since the start of the pandemic, including at least 128 deaths, according to the latest data from the health ministry.