November 2. A potentially faster-spreading “sub-lineage” of the coronavirus Delta variant named AY.4.2 has been spotted by labs in at least 8 states, and health authorities in the United Kingdom say they are investigating a growing share of cases from this strain of the virus.
Labs in California, Florida, Maryland, Massachusetts, Nevada, North Carolina, Rhode Island and Washington state, plus the District of Columbia, have so far spotted at least one case of AY.4.2.
While it may spread somewhat faster, health authorities have not found evidence of more severe illness caused by the variant, and they say current vaccines remain effective against it.
The sub-lineage has remained a small fraction of circulating cases in the U.S. for several weeks, but American health officials say they are already ramping up efforts to study the new Delta variant descendant.
Scientists have already turned up worrying combinations of mutations in other sub-lineages of Delta called AY.1 and AY.2, which like AY.4.2 have also sometimes been interchangeably called “Delta plus” variants.
In the U.K., AY.4.2 has climbed to more than 11% of cases of the Delta variant. Health officials there say the variant does not appear to have led to a “significant reduction” in vaccine effectiveness or an uptick in hospitalizations, but it could be spreading faster because of “slightly increased biological transmissibility.”
The Centers for Disease Control and Prevention estimates that AY.4.2 has made up less than 0.05% of circulating cases in the U.S. for several weeks, according to an agency spokesperson. Grouped together, CDC estimates that the Delta variant and its sub-lineages has been virtually 100% of cases in the U.S. for months.
Outbreak.info had previously counted AY.4.2 sightings in at least 35 states. However, Gangavarapu said a bug in the “Pangolin” system used to generate reports of variants had resulted in some false positives for the sub-lineage showing up in some tallies.