State health officials have detected another highly transmissible variant of COVID-19 originally found in South Africa in an Oahu resident with no travel history.

“This is the first instance of this South African variant that we’ve found,” Gov. David Ige told the Honolulu Star-Advertiser’s Spotlight Hawaii livestream program Monday.

An undisclosed number of household contacts also have tested positive for the virus — and are assumed to have the same variant, said Dr. Sarah Kemble, acting state epidemiologist at the Department of Health, which is still investigating the resident’s workplace.

“That means there has already been some circulation in our community even if it may be limited at this time. That means we do have to keep an eye out for these variants because they’re going to be out there,” she said.

The DOH State Laboratories Division also has found two more cases of the highly contagious variant known as B.1.1.7, originally found in the United Kingdom. Eight people with the U.K. variant have been identified in Hawaii since early February, including the most recent cases involving two Oahu residents, one of whom traveled to the mainland and then infected a household member.

“Neither of these variants is clearly associated with more severe disease, but they have been spreading more rapidly in the areas where they are occurring,” Kemble said, adding that the public health strategy remains the same — mask wearing, social distancing, hand washing and getting vaccinated for COVID-19. “The key to the variants is to control the virus. Slowing down the spread gives them less chance to further mutate and potentially cause additional problems.”

Besides a mutation that increases infectiousness, the new South African strain, known as B.1.351, has a “separate mutation … that might make it less responsive to the antibodies,” that develop due to infection or vaccination, said Dr. Edward Desmond, director of the State Laboratories Division, which noted that this is the first time that both mutations have been found in one virus.

“There have been a few instances where a person who was previously infected with a strain that did not have the … mutation then was subsequently infected by a new strain that had this … mutation like the South African variant,” Desmond said. “That creates some concern that immunity is not absolute when you have one of these variant strains.”

However, the one-shot Johnson & Johnson vaccine, which the state received last week, has proved effective in preventing serious disease and death in South Africa, where the strain is predominant.

“We obviously want to avoid to the extent possible having the variant take over and raise the level of concern about how well vaccines are going to work,” Kemble said, adding that so far the vaccines still seem to work on the variant. “The more people that are vaccinated, you don’t even get a foothold for these viruses, they don’t have a chance to pose that threat.”

The state is racing to immunize the population as more variants emerge in the islands. The DOH this week began administering shots to residents 70 and older and expects to open up vaccinations to those 65 and up as early as this month. Hawaii has so far vaccinated 496,050 people against COVID-19, Lt. Gov. Josh Green wrote in an online post.

“Research shows community mitigation measures are effective in reducing the risk of transmission of even the most aggressive variants,” Health Director Libby Char said in a news release. “This means wearing masks, maintaining physical distance and washing hands is more important than ever. The effectiveness of vaccines in preventing serious illness or death means we should get vaccinated as soon as it is our turn.”

Health officials reported 45 new coronavirus infections, bringing the state’s total since the start of the pandemic to 27,935 cases. The statewide death toll remains at 445 with no new COVID-19 fatalities.

Meanwhile, the Centers for Disease Control and Prevention said Monday that Americans who are fully vaccinated can gather indoors without having to mask up or physically distance themselves, including socializing with those whose risk is low for severe disease.

“It’s still important to be very cognizant of who may still be at risk. If you’re gathering with people who are not vaccinated, you have to make some risk decisions,” Kemble said. “This is really still limited to small gatherings in private spaces. In public spaces we need all the layers of mitigation we can get right now as people continue to be vaccinated in the entire population.”

Honolulu Mayor Rick Blangiardi said he agrees with the CDC guidelines and is looking forward to “safely getting together with friends and family who have been vaccinated or who are not high risk.”

“We know that COVID-19 vaccines are effective at protecting people from getting sick,” he said. “Even with the new recommendations, it is important to continue wearing a mask, keeping your distance and avoiding large social gatherings, because we know those measures are helping keep our case numbers low.”