A new COVID-19 subvariant that is spreading rapidly in the United Kingdom is already here in Massachusetts, health experts say.
Known as AY.4.2, the so-called “delta plus” variant is believed to be even more contagious than the highly transmissable delta variant. One expert said it could be 10% to 15% more contagious than delta.
So far, the mutation has been detected in Massachusetts, Washington, D.C., California, North Carolina and Washington state, according to Outbreak.info.
Concerns about delta plus are currently very high in the U.K., which is seeing a surge in cases. The new subvariant had accounted for about 6% of all cases at last check.
But U.K. government health officials have said it’s too early to tell whether the mutation poses a greater risk to public health than the delta variant, which itself is significantly more infectious than the original COVID-19 strain.
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Although AY.4.2 is being monitored, it has not been classified as a “variant under investigation” or a “variant of concern” by the WHO — that is, it has not been identified as having genetic changes that are expected to affect virus characteristics such as transmissibility, disease severity, immune escape, diagnostic or therapeutic escape.
It also has not been confirmed that it causes significant community transmission or multiple COVID-19 clusters. Still, that status could change following further monitoring and if it continues to be sequenced in an increasing number of cases.
Health officials are remaining calm about the delta subtype, for now, noting that it’s crucial to keep an eye on the mutation but not to panic.
Commenting on “delta plus” last week, U.S. Centers for Disease Control and Prevention Director Rochelle Walensky noted that “in particular the AY.4.2 variant has drawn some attention in recent days.” She added that: “we have, on occasion, identified this sub lineage here in the United States, but not with recent increase frequency or clustering, to date.”