The update said that outside of India, the United Kingdom has reported the largest number of cases sequenced as B.1.617 sub-lineages, and recently designated B.1.617.2 as a "national variant of concern".
Health agencies escalate or de-escalate variants as scientific evidence evolves, a CDC spokesperson said in a statement, adding that US classifications of variants may not align with those of the WHO "since the importance of variants may differ by location".
As of May 11, over 4,500 sequences have been uploaded to GISAID and assigned to B.1.617 from 44 countries in all six WHO regions, the global health body said in its latest weekly epidemiological update published on Tuesday. Based on reports from hospitals, Kang said it appeared that B.1.617 was causing more severe disease but that, again, there was insufficient data to draw conclusions. The variant, it added, had "increased transmissibility" and has been found in 44 countries.
The Indian variant is the fourth classified "of concern" by the World Health Organization, after the variants detected in Britain, Brazil and South Africa.
'We are classifying this as a variant of concern at a global level, ' Maria Van Kerkhove, WHO technical lead on COVID-19, told a briefing.
That danger stems from a variant's higher transmissibility, lethality and resistance to vaccines, or either of them.
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Once that immune response is triggered, antibodies are produced, which protect people from being infected should the virus enter their system in the future.
After India, the B.1.617 variant has been majorly found in the UK. It has been added to the list as it seems to be transmitting faster and more easily than the original virus and, thus, hints towards the "rapid increases in prevalence in multiple countries".
She also pointed to early studies "suggesting that there is some reduced neutralisation", meaning that antibodies appeared to have less impact on the variant in small-sample lab studies.
Viruses in the B.1.617 lineage were first reported in India in October 2020.
The resurgence in COVID-19 cases and deaths in India have raised questions on the potential role of B.1.617 and other variants such as B.1.1.7 in circulation.
It has for some time been feared that B.1.617 - which counts several sub-lineages with slightly different mutations and characteristics - might be contributing to the alarming spread.
But according to Outbreak.info, which track the result of global genetic sequencing - a test performed to see what mutations a viral sample contains - suggest that about two percent of USA samples tested Monday were positive for B.1.617.2's mutations.
'Even though there is increased transmissibility demonstrated by some preliminary studies, we need much more information about this virus variant and this lineage and all of the sub-lineages, ' she said.