The WHO has now concluded that only one sub-lineage strain of the Covid-19 Delta variant first detected in India is considered "of concern", while two other strains had been downgraded.
The B.1.617 variant of the virus, which is considered to be partly responsible for the ferocious second wave in India, has now been termed a triple mutant variant since it is split into three lineages.
The WHO last month declared the entire strain a "variant of concern" (VOC), but on Tuesday, it said now only one of the sub-lineages fits into this category. The fact that two of the sub-lineages are not as dangerous comes as a big relief for India.
"It has become evident that greater public health risks are currently associated with B.1.617.2, while lower rates of transmission of other lineages have been observed," the World Health Organization said in its weekly epidemiological update on the pandemic.
The B.1.617.2 variant remains a VOC, along with three other variants of the virus, , such as those found in the UK and South Africa, that are seen as more dangerous than the original version because they are more transmissible, deadly or have the potential to get past some vaccine protections.
"We continue to observe significantly increased transmissibility and a growing number of countries reporting outbreaks associated with this variant," the UN agency said.
"Further studies into the impact of this variant remain a high priority for WHO."
A new hybrid variant announced by Vietnam's health authorities on Saturday appears to be a variation of Delta.
"We know that the B.1.617.2, the Delta variant, does have increased transmissibility, which means it can spread easier between people," WHO’s Covid-19 expert Maria Van Kerkhove told journalists in Geneva on Tuesday.
The B.1.617.1 sub-lineage has meanwhile been downgraded to a "variant of interest," and dubbed Kappa.
And the B.1.617.3 is now not even considered of interest, WHO said, since "relatively few reports of this variant have been submitted to date."
WHO has decided to refer to Covid-19 variants using Greek letters, in order to avoid the possible stigmatisation associated with referring to them with names of the countries where they were first detected.