ST. LOUIS — Officials who monitor Missouri’s wastewater, which can give the first hints of emerging variants of the coronavirus, say they’ve detected the presence of the mu variant in only a handful of samples — and none recently.
The World Health Organization last week named mu and classified it as a “variant of interest.” It’s the fifth coronavirus variant the organization is monitoring. Preliminary evidence suggests it has the potential to partially evade protection from vaccination.
Since being discovered in Colombia in January, the mu variant has spread to nearly four dozen countries. In the U.S., nearly 5,300 cases have been reported in every state except Nebraska.
California has reported the highest number with 384. A total of 167 of those cases were found in Los Angeles County, the New York Daily News reported.
Only five cases of the mu variant have been detected through sequencing of samples in Missouri, state health officials say. Two were detected in May, one in June, one in July and one in August.
The U.S. Centers for Disease Control and Prevention has not yet classified the mu variant, which has not been able to gain a foothold against the highly infectious delta variant that has caused cases and hospitalizations to rise across the country.
Data shows the U.S. saw its peak of the mu variant in mid-July, when it made up nearly 1.5% of cases. Now, it’s less than 1%.
The Coronavirus Sewershed Surveillance Project, based at the University of Missouri-Columbia, tests over 60 community wastewater facilities serving about 3.5 million residents across Missouri.
Researchers with the project see a similar trend in Missouri, with the mu variant appearing to fizzle out.
What researchers suspect was the mu variant first appeared in the wastewater in late June, said University of Missouri molecular biology professor Marc Johnson. It appeared again at one site in July and another in early August.
“At the same time, delta (variant) has pretty much taken over in terms of lineages we see,” Johnson said. “It’s the only linage I’ve seen in Missouri in several weeks.”
Missouri is one of the first states to initiate wastewater testing last summer, and it is one of the largest scale projects in the U.S.
“As more and more people get vaccinated, these lineages with some level of vaccine resistance are going to be important things to watch,” Johnson said.
Delta is currently outrunning the mu variant, he said, but that could change.
“Once delta eventually crests, who knows, maybe mu will make a move,” Johnson said, “it’s hard to predict.”
If mu becomes more serious and begins to overtake other variants such as delta, it could be upgraded to the highest “variant of concern” classification.
BJC HealthCare infectious disease specialist Dr. Hilary Babcock said the best defense is for as many people as possible to get vaccinated.
“Every time the virus replicates and spreads into another person, it can mutate, and it can evolve into a different variant,” Babcock said. “And the only variants that are going to get a foothold against delta are the ones that are more transmissible, more able to evade vaccines and more able to evade our preexisting immunity.”
In addition to delta and mu, the three other variants being tracked by WHO are alpha, beta and gamma. Each is named for a letter in the Greek alphabet.