Another variant of COVID-19 has reached Dallas County, health officials say.
The variant, known as B.1.621, or mu, was added to the World Health Organization’s variants of interest list on Aug. 30.
A strain is considered a variant of interest if it causes significant community transmission or has genetic features that indicate it may affect factors like disease severity and resistance to vaccines or treatment. It’s a step below variants of concern, which are circulating more widely.
While health experts say the new variant is not yet a threat, it’s important to monitor the emerging strain. Here’s what you need to know.
Where did the mu variant come from?
The mu variant was first detected in Colombia in January, according to the WHO.
The variant has since spread to 39 countries, and its prevalence Colombia and Ecuador has “consistently increased,” the WHO says.
How widespread is it?
The delta variant still made up more than 99% of cases in the U.S. as of the end of August, meaning the mu variant is not yet cause for concern.
An estimated 2,400 cases of the variant have been detected in the United States as of early September, according to the Global Initiative on Sharing All Influenza Data, a database of coronavirus and influenza viruses around the world.
All but one state, Nebraska, have recorded cases of the strain, according to data compiled by The Center for Viral Systems Biology at Scripps Research.
In Dallas County, health officials have recorded five cases of the mu variant, said Dr. Jeffrey SoRelle, an assistant instructor in the department of pathology at UT Southwestern Medical Center who is co-leading an effort to analyze COVID-19 tests.
He said the cases were detected between late July and early to mid-August, but since analyzing COVID-19 tests takes one to two weeks to complete, it’s possible more could pop up.
Not all of the cases were travel-related, indicating community spread is occurring, he said. UTSW researchers don’t yet know if any of the five cases were among vaccinated individuals.
While the Centers for Disease Control and Prevention have yet to give the mu variant an official classification, Dr. Anthony Fauci, the top U.S. infectious disease expert, said the United States is actively monitoring it.
What’s different about the mu variant?
The mu variant contains mutations on the spike protein found on the virus that causes COVID-19, said SoRelle.
The mutations are similar to those that were found on the B.1.1.7, or alpha, variant that originated in the United Kingdom and the P.1, or gamma, variant first identified in travelers from Brazil.
Before the highly contagious delta variant came along, the alpha variant was thought to be more transmissible than the 2020 strain of COVID-19. It’s likely that the transmissibility of mu lies somewhere in between alpha and delta, SoRelle said.
“So far, we’ve seen [mu] in the U.S., in Connecticut and the Virgin Islands, being present in prevalence levels as high as 8%,” he said. “But it appears that it does not out-compete delta, and more recently levels [of mu] have actually been decreasing quite a bit in those areas.”
Do vaccines work against the variant?
Fauci said that the mu strain of COVID-19 “has a constellation of mutations that suggests it would evade certain antibodies,” but that more data is needed to know for sure what that means, The New York Times reported.
He also said that the current vaccines were still effective against other COVID-19 variants with similar characteristics.
The WHO likewise says that preliminary data found that COVID-19 vaccines may not be as effective against the strain, but that more studies are needed to confirm that finding.
Pfizer told The Washington Post that it was studying its vaccine’s effect on the variant and planned to collect data for peer review.
“To date, we are encouraged by both the real-world data and laboratory studies of the vaccine and see no evidence that the virus or circulating variants of concern regularly escape protection,” Pfizer spokesperson Kit Longley said.
What does this mean for Dallas County?
SoRelle and the team at UT Southwestern only sequence COVID-19 tests from UT Southwestern providers, meaning they still have a somewhat limited view of the actual prevalence of COVID-19 variants.
But he said when compared to statewide numbers, the team’s analysis of tests matches up with overall trends.
He said while the variant’s presence in places like Colombia is concerning, the best way to tell how the strain will behave in Dallas County is to monitor trends in places with similar transmission levels.
“The best comparison for Dallas would be a place in the United States that has both delta and the new variants,” SoRelle said. “And in those situations, the delta is actually overtaking them.”
People should view the presence of the mu strain as a reason to get vaccinated if they haven’t, or as a reason to keep up with booster recommendations as they roll out toward the end of the month, SoRelle said.
“In this case, you didn’t have as much transmissibility, so it’s not going to spread very much and have immune resistance, but you could have a future one [variant] that does,” he said. “This is just more evidence that it’s a good reason to go ahead and get a booster shot if it’s available to you.”