'Hold tight and enjoy our low positivity rate at the moment'

As COVID cases rise in parts of Asia and Europe, the virus’ impact in the Charleston area is classified as “minimal” by the Medical University of South Carolina’s COVID-19 tracking team. “I think the main message is hold tight and enjoy our low positivity rate at the moment,” said scientist Julie Hirschhorn, Ph.D., director of Molecular Pathology at MUSC.

Currently, only about 3% of samples tested for COVID at MUSC are positive, meaning the people they came from are actually infected with the coronavirus. But the positivity rate is rising in some other places across the world, raising questions about what’s ahead for everyone else. 

“I think we will continue to see country-specific waves across the world that may be due to differences in vaccine type and schedule; waning immunity, both natural or from vaccine and easing of protective measures as well as changes in testing schemes.”

Hirschhorn, an associate professor in the College of Medicine, said the United States’ recent Omicron surge should offer some protection here. “We would expect to have a lot of natural immunity across the country that should last for a little while.”

But the Omicron sub-variant BA.2, about 30% more transmissible than Omicron, is spreading in the U.S., and it may catch some people off guard. “There is always risk of catching the Omicron sub-variant if individuals are not up to date with their vaccination schedule or have not recently had COVID-19.” 

BA.2 has not shown in testing at MUSC. “Not yet,” Hirschhorn said. “I am hopeful that we will get a couple of months of reprieve from a high burden of disease in our population given the natural and vaccine immunity in our community.”

Hirschhorn’s team is also keeping an eye out for what’s being called Deltacron. “Because much of the world had a large overlap of Delta and Omicron variants, some patients may have been infected by both Delta and Omicron variants at the same time, also called co-infection,” Hirschhorn said.

 

“When two different variants are present in a single individual, there is the very rare risk of recombination of the virus, meaning that a single human host cell was infected with both variants of the same virus at the same time and during the replication process, when the virus makes copies of itself, part of one genome of one virus will combine with part of the genome of the other variant.”

But there aren’t many documented and verified cases of Deltacron, Hirschhorn said. “At this time, there does not appear to be any reason for concern with the recombinant variants. There are only a handful of cases and very little information about how these variants affect the individuals infected. At this time, the variants are rare and have not spread in any significant way.”

She said that monitoring will get trickier as circumstances change. “For example, the United Kingdom has been an international leader in sequencing and identification of new variants of COVID-19, and they are starting to scale back their sequencing surveillance systems as well as reducing their testing strategies.”

In South Carolina, the Department of Health and Environmental Control recently shifted from daily to weekly COVID data reporting and closed more testing sites. Demand is down as the Omicron surge wanes and a lot of the people who do want to be tested for COVID do it at home.

“The reduction in testing and the increase of at-home testing will provide fewer samples for sequencing surveillance to look for new variants. This is important to keep in mind as we look at testing and surveillance statistics because depending on who is getting tested, the picture of what is going on with COVID-19 could get skewed and in general we may have less data,” Hirschhorn said.

But MUSC will keep checking every potential COVID case that comes its way. “We will continue to offer COVID-19 testing and perform sequencing surveillance on our positive cases across our health care system.”