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The delta variant, which has spread rapidly across the country in recent weeks, has likely become the dominant COVID-19 strain in South Carolina, although the exact number of cases is unknown.
The highly transmissible variant, first identified in India, accounts for more than half of the coronavirus cases the state’s public health laboratory has identified through genomic sequencing, according to the S.C. Department of Health and Environmental Control.
The rapid ascension of delta, which made up only 5% of South Carolina’s COVID-19 cases last month, is “incredibly concerning,” DHEC spokesman Derrek Asberry said.
“Given that the delta variant has proven to be more transmissible than prior strains, the spread of it could increase faster and/or to a larger degree,” he said.
DHEC officials have said for weeks that South Carolina, like other states with low vaccination rates, was susceptible to an outbreak from delta, but the variant’s role in the state’s recent case spike had only been speculated.
Sequencing data released Monday by DHEC provides strong indication that many of the 5,600 COVID-19 cases reported in South Carolina over the past two weeks have been delta infections.
According to DHEC, roughly 86% of the 74 cases its public health lab sequenced between July 1 and July 15 are variants of concern, a term the U.S. Centers for Disease Control and Prevention uses to describe the alpha (Britain), beta (South Africa), delta (India) and gamma (Brazil) strains of SARS-CoV-2.
Delta accounted for 63% of the variants of concern identified in South Carolina over that span, meaning that approximately 40 of 74, or 54%, of coronavirus cases sequenced this month have been delta.
Total number of delta cases unknown
As of July 14, DHEC had identified 54 delta cases in the state, roughly 70% of which were concentrated in the Midlands and Pee Dee regions.
That’s a more than fourfold increase in the variant compared to the week prior, an indication the variant is spreading quickly.
However, because only a tiny fraction of all confirmed coronavirus cases are genomically sequenced, the true number of delta cases in South Carolina is not known.
Spread of the variant, which is facilitated by South Carolina’s large number of unvaccinated residents, is likely responsible for the recent uptick in COVID-19 cases, state health officials said.
Coronavirus cases in the state have increased each of the last four weeks, with weekly infections more than tripling over that period, from 1,050 to 3,565, according to DHEC data.
Delta’s transmissibility — the variant is between 40% and 60% more transmissible than alpha, which itself is 50% more transmissible than the wild-type coronavirus strain — and the state’s sub-50% vaccination rate are likely to blame, Asberry said.
“Much of the state is unvaccinated, and traveling and mask-wearing is not as frequent as it once was or needs to be,” he said.
The size of the COVID-19 surge South Carolina sees in the weeks ahead largely depends on how many more residents get vaccinated and how many of those unvaccinated take safety precautions like wearing masks and maintaining physical distancing, Asberry said.
Vaccination, he said, remains key to stemming the delta variant’s rise and ending the pandemic.
All three COVID-19 vaccines on the market in the U.S. are considered highly effective against the delta strain, if administered as recommended.
A considerable number of people nationwide, including more than 200,000 in South Carolina, remain vulnerable to delta infection, however, because they haven’t completed their inoculation series.
Roughly 10% of South Carolinians are at least a week late for their second shot of the Pfizer or Moderna vaccine, and about 90% of those are more than a month late, state health officials said.
While delaying the second dose of either vaccine does not appear to weaken one’s immune response, research shows that partially vaccinated individuals fare significantly worse against COVID-19 variants like delta.
Statewide, 49.7% of eligible South Carolina residents have received at least one dose of vaccine and 43.8% are fully vaccinated.