- Luke O’Neill
- The Conversation*
The World Health Organization (WHO) has added a new variant of the coronavirus to its watch list. It is called the Mu variant, classified as a variant of interest (VOI). What this term means is that Mu has genetic differences from other known variants and is causing infections in several countries, therefore, it may pose a specific threat to public health.
It is possible that genetic alterations of the Mu variant could make it more transmissible, responsible for more serious diseases and better able to escape the immune response driven by vaccines or infection with other variants. This, in turn, can make the variant less susceptible to treatments.
Note the word “may”. A variant of interest (VOI) is not a variant of concern (VOC), which is a variant that has been proven to acquire one of these traits, making it more dangerous. Mu is being closely monitored to see if it should be reclassified as a VOC. We have to hope not.
There are four other VOIs being monitored by WHO — Eta, Iota, Kappa and Lambda — but none of them have been reclassified as a VOC. This can also happen with Mu, but you have to wait for more data.
What makes Mu particularly interesting (and worrisome) is that she has what the WHO calls a “constellation of mutations that indicate potential properties of immune escape.” In other words, it has the hallmark of being potentially able to circumvent existing vaccine protection.
Where is Mu spreading?
Mu was first identified in Colombia in January 2021, when it received the designation B1621. It has since been detected in 40 countries, but it is currently estimated to be responsible for only 0.1% of infections worldwide.
Mu has been far more prevalent in Colombia than anywhere else. When we analyzed the coronavirus samples that were genetically sequenced, 39% of those analyzed in Colombia were Mu — although no Mu samples have been recorded there in the past four weeks.
In contrast, 13% of the samples analyzed in Ecuador were Mu, with the variant representing 9% of the samples sequenced in the last four weeks, while in Chile just under 40% of the samples sequenced were Mu in the last month. This suggests that the virus is no longer circulating in Colombia, but is being transmitted in other nearby South American countries. In Brazil, two cases were confirmed in the State of Amazonas.
So far 45 cases have been identified in the UK through genetic analysis and appear to have come from abroad. However, as not all covid-19 cases end up being sequenced to see which variant they are, it is possible that the prevalence of Mu in the UK is higher.
How dangerous is this situation?
Mu has a mutation called P681H, first identified in the Alpha variant, which is potentially responsible for faster transmission. However, this study is still in the pre-print phase, which means its findings have yet to be formally reviewed by other scientists. We are not sure of the effects of P681H on virus behavior yet.
Mu also has the E484K and K417N mutations, which are associated with the ability to evade antibodies against the coronavirus: the evidence for this is more concrete. These mutations also occur in the Beta variant and therefore it is possible that Mu could behave like Beta, against which some vaccines are less effective.
Mu also has other mutations — including R346K and Y144T — whose consequences are unknown, hence the need for further analysis.
But can Mu really escape pre-existing immunity? For now, there is only limited information on this, with a study from a laboratory in Rome showing that the Pfizer-BioNTech vaccine was less effective against Mu compared to other variants when tested in a laboratory experiment. Despite this, the study still considered the protection offered against Mu by the vaccine to be robust. In fact, we still don’t know if Mu mutations will translate into increased infection and disease.
However, impressive reports about Mu have surfaced around the world. In late July, a Florida news outlet reported that 10% of samples sequenced at the University of Miami were Mu. In early August, Reuters reported that seven fully vaccinated residents of an asylum in Belgium had died in the midst of an outbreak of the Mu variant. However, these are very restricted situations of variant behavior.
What happens now?
Mu is the first new variant to be added to the World Health Organization list since June 2021.
When a variant is classified as “of interest”, the World Health Organization performs a comparative analysis of the characteristics of the new variant, assessing how it compares to others that are also being monitored, asking its member countries to collect information about the incidence and effects of the variant. This is in progress.
The classification of Mu as a variant of interest reflects widespread concern about the possibility of new variants emerging that could be problematic. The more transmissible Delta variant, which is dominating in many countries, especially among the unvaccinated, shows how quickly and significantly viral variants can change the course of the pandemic.
Every time the virus reproduces inside someone, there is a chance that it will mutate and a new variant will emerge. It’s a random process, a bit like rolling dice. The more you cast them, the greater the chance of new variants appearing. The main way to contain variants is global vaccination.
The emergence of Mu reminds us how important this vaccination goal remains. Many people, especially in developing countries, remain unvaccinated. We must get vaccines to these countries as quickly as possible, both to help vulnerable people and to prevent the emergence of new strains. Otherwise, our exit from the pandemic will be delayed, possibly for months and months.
*Luke O’Neill is a biochemist and professor at Trinity College Dublin
This article was originally published on the academic news site The Conversation and republished here under a Creative Commons license. read here the original version (in English).
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