The World Health Organization recently classified the COVID-19 mu variant as a "variant of interest." Spectrum News looked into what health professionals know about it — and the impact the mu variant is having in Florida. Here are five things to know:

1. What is the mu variant?

According to the World Health Organization's COVID-19 Weekly Epidemiological Update published on August 31, mu is a strain of COVID-19 that was first identified in January in Colombia.

"The Mu variant has a constellation of mutations that indicate potential properties of immune escape," the report reads.

Dr. Nicole Iovine, an infectious disease specialist and chief hospital epidemiologist with UF Health in Gainesville, said that means current vaccines might not provide a higher level of protection against mu compared to other variants.

"We don't have a clear sense of how many vaccinated people, for example, would be expected to develop a breakthrough infection with mu, let's say, compared to delta or one of the other variants," Iovine said.

The WHO classified mu as a variant of interest.

2. What's the difference between a 'variant of interest' and a 'variant of concern?'

Unlike mu, some variants, including delta, have been classified as variants of concern by the WHO.

Dr. Michael Teng, a virologist and associate professor of medicine with the University of South Florida, compared the classification system to a traffic light.

"On the green level, the variant of interest is what mu is, and that's the kind of lowest classification. That's a variant that's actually done something out in nature that the WHO and CDC want to keep track of," Teng said.

In mu's case, Teng said that action was becoming the dominant variant in Colombia.

"Variants of concern are kind of like the amber light," said Teng. "So, that would be like delta, like alpha and beta and gamma — variants that have actually taken over at some point in a number of countries and that have some characteristics that are concerning."

Teng said examples are the high level of transmission of the alpha and delta variants.

3. How widespread is the mu variant?

Mu appears to be very rare right now. According to the online database outbreak.info, mu makes up less than half a percent of global COVID cases. CDC data shows it made up just .1% of US cases last week. Florida does have more cases of the mu variant than any state except California. Outbreak.info shows 305 cases have been reported here. Teng said direct flights from Colombia to Florida are one possible reason that number is higher than other states. Iovine said it's important to keep that total in perspective. "If you look at the overall number of cases that we're having in Florida...305 is very little, relatively speaking," she said. 

4. What impact could the delta variant have on the spread of mu?

The WHO said it plans to monitor mu in South America, particularly how it co-circulates with delta.

"We don't know how well it competes with delta," said Teng. "Delta is significantly higher transmissibility than any of the other variants than we've seen previously, and so we've seen delta basically take over across the world."

Iovine said unless cases of delta diminish, mu will likely have a hard time spreading.

"If you were to have delta and mu in a boxing ring, delta is going to win. It's much more transmissible, reaches much higher levels. So, delta is always going to win out in that fight," Iovine said.

5. Do we need to be particularly concerned about mu?

Teng and Iovine say no. According to Teng, very recent evidence suggests that despite its mutations, mu is still susceptible to immunity built up from vaccines.

"We had a little bit of vaccine efficacy drop against beta and gamma, and it looks like it's less with mu than it was with gamma. So, the vaccine works better against mu than it does with beta or gamma," Teng said.

Iovine does offer words of caution.

"One thing I would say, though, that we've learned through this pandemic is that things can change. As long as there are a lot of unvaccinated people out there, the virus will continue to mutate, and we will continue to have variants. I think the nightmare scenario would be if a variant were to emerge that had the transmissibility of delta and have significant vaccine escape."