UW Medicine tracking new mu variant in Washington

Cases driven by the delta variant are still on the rise, but now health officials are starting to closely monitor another variant called the mu variant.

Its mutations are raising concerns that it may be more resistant to COVID-19 vaccines. According to outbreak.info, a Scripps Research website, the mu variant has spread to 49 states, including Washington state.

UW Medicine’s virology labs handle the bulk of COVID-19 genetic sequencing in the state.

Researchers said the way the mu variant mutated has scientists paying close attention.

“There are a couple of mutations that have been shown in other studies to be associated with either increased transmissibility, or immune escape. So that’s one of the reasons why it is concerning,” said Pavitra Roychoudhury, an instructor with UW Medicine’s lab medicine and pathology department.

Because of its potential to evade certain antibodies, including possibly those generated by a vaccine, the World Health Organization just added mu to its “variants of interest” short list last week, bringing the total to five variants on that list.

Adding to the concern, the variant also surged in Columbia, which is where it first emerged. “The prevalence in Colombia (39%) and Ecuador (13%) has consistently increased,” the WHO confirmed in its weekly update. WHO also pointed out that the mu variant has declined on a global level.

Top infectious disease doctor, Anthony Fauci, addressed the variant last week in a briefing.

“We’re keeping a very close eye on it. It is really seen here, but it is not at all even close to being dominant,” Fauci said. “We don’t consider it an immediate threat right now.”

The variant, also known as B.1.621, is a variant UW Medicine has actually been tracking in the state since April.

“We sort of knew mu before mu was famous, I would say,” Roychoudhury said.

Since April, the mu variant has been circulating at a low rate — making up less than a half percent of sequenced cases here. Still, it’s something the state is monitoring.

In August, the Washington Department of Health documented 14 sequenced cases of the mu variant out of 3,442 cases sequenced, or 0.41% of all sequenced cases. (About 20% of all COVID-19 cases for the month were sequenced.)

The mu variant is not currently reported as part of the DOH’s COVID-19 data dashboard because it’s currently not considered a variant of concern or variant of interest by the Centers for Disease Control and Prevention. The DOH stated it is tracking the variant for surveillance, and it has not seen the mu variant increase over time.

Outbreak.info reportsed 111 total cases of the mu variant in Washington. Only Nebraska showed zero cases as of Tuesday.

Roychoudhury said it’s hard to tell if the mu variant will be able to gain any foothold over the delta variant, which made up 98.2% of COVID-19 cases in Washington last month.

“There are certain variants that lay at low levels for a while,” she said.

But Roychoudhury said your best bet to protect yourself against this new variant is to get vaccinated.

“Even if a particular variant shows some diminished efficiency against the vaccines, it’s still going to protect you from being very sick or dying,” she said.

Studies are underway to determine how well existing vaccines protect against the mu variant.