The World Health Organization (WHO) has added another variant of the coronavirus to its watch list. It’s called mu and it’s been designated a variant of interest (VOI). This means that it has genetic differences from the other known variants and is causing infections in multiple countries, so it could pose a particular threat to public health.
Mu’s genetic changes may make it more transmissible, allow it to cause more serious disease, and make it better able to escape the immune response elicited by vaccines or infection with earlier variants. This, in turn, could make you less susceptible to treatments.
Note the word could. A VOI is not a variant of concern (VOC), it is a variant that has been shown to acquire one of those characteristics, making it more dangerous and therefore more important. Mu is being closely watched to see if it should be designated a VOC. Hopefully it is not.
There are four other VOIs that are being monitored by the WHO – eta, iota, kappa and lambda – but none of them have been reclassified as VOCs. That could be the case for mu as well, but we have to wait for more data.
What makes mu particularly interesting (and concerning) is that it has what the WHO calls a “constellation of mutations that indicate potential immune escape properties.” In other words, it has the distinctive features of being able to circumvent existing vaccine protection.
Where is it spreading?
Mu was first seen in Colombia in January 2021, when it was given the designation B.1621. Since then it has been detected in 40 countries, but is currently believed to be responsible for only 0.1% of infections globally.
Mu has been much more prevalent in Colombia than anywhere else. If we look at the coronavirus samples that have been genetically sequenced, 39% of those analyzed in Colombia have been mu –although no samples have been registered there in the last four weeks–.
On the contrary, 13% of the samples analyzed in Ecuador have been mu, and this variant represents 9% of the samples sequenced in the last four weeks, while in Chile slightly less than 40% of the samples sequenced have turned out to be. 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.
So far, 45 cases have been identified in the UK through genetic testing, and they 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 it?
The key questions are whether mu is more transmissible than the currently dominant variant, delta, and whether it can cause more serious disease.
Mu has a mutation called P681H, first reported in the alpha variant, which is potentially responsible for faster transmission. However, this study is still in prepublication format, which means that its conclusions have not yet been formally reviewed by other scientists. We still cannot be sure of the effects of P681H on the behavior of the virus.
Mu also has the E484K and K417N mutations, which are associated with the ability to evade coronavirus antibodies. The evidence on this is more concrete. These mutations also occur in the beta variant, so it is possible that mu behaves like beta, against which some vaccines are less effective.
Mu also has other mutations, such as R346K and Y144T, the consequences of which are unknown, hence the need for further analysis.
But can mu really evade pre-existing immunity? There is only limited information on this so far, 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 found the protection offered against mu by the vaccine to be robust. We really don’t know yet whether mu mutations will lead to increased infection and disease.
However, surprising reports have appeared about mu. In late July, a Florida news channel reported that 10% of the samples sequenced at the University of Miami were mu. In early August, Reuters reported that seven fully vaccinated residents of a nursing home in Belgium had died from an outbreak of mu. However, these are limited snapshots of the variant’s behavior.
What will happen next?
Mu is the first new variant to be added to the WHO list since June.
When a variant of interest is designated, WHO conducts a comparative analysis of the characteristics of the new variant, assessing how it compares with others that are also being monitored, asking its member states to collect information on incidence and effects. of the variant . This is taking place today.
The designation of mu as VOI reflects widespread concern that new variants may emerge that may be problematic. The more transmissible delta variant, which is gaining ground in many countries, especially among the unvaccinated, shows how quickly and how significantly viral variants can change the course of the pandemic.
Every time the virus reproduces inside a person, there is the possibility that it will mutate and a new variant will emerge. It’s a numbers game. It is a random process, a bit like rolling the dice. The more runs there are, the greater the chance that new variants will appear. The main way to stop the variants is global vaccination.
The appearance of the mu reminds us how important that goal continues to be. Many people, especially in developing countries, remain unvaccinated. We must get vaccines to these countries as soon as possible, both to help vulnerable people there and to prevent new variants from emerging. Otherwise, our exit from the pandemic will be delayed, possibly for months.
Luke O’Neill, Professor, Biochemistry, Trinity College Dublin
This article was originally published on The Conversation. Read the original.
