The World Health Organization on Tuesday said that only one strain of the coronavirus variant first detected in India was now considered “of concern”, while two others had been downgraded.

On Monday, the global health body announced a new naming system for variants of Covid-19 to simplify pronunciation and avoid the possible stigmatisation associated with referring to them with the name of the countries where they were first detected. The B.1.617.2 variant of the virus that emerged in India has been labelled Delta.

Viruses mutate all the time, resulting in millions and millions of new variants. However, what has made scientists worry about B.1.617 is the presence of three mutations – E484Q, L452R and P6814 – the reason why some are referring to it as a “triple mutant” variant.

Last month, the WHO declared the entire strain a “variant of concern”, but on Tuesday it said that only one of the sub-lineages deserved this label. “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 body said in its weekly epidemiological update on the coronavirus pandemic.

The B.1.617.2 variant, along with strains first found in United Kingdom, South Africa and Brazil, are seen as more dangerous than the original version because they are more transmissible.

“We continue to observe significantly increased transmissibility and a growing number of countries reporting outbreaks associated with this variant,” the UN agency said about the Delta strain. “Further studies into the impact of this variant remain a high priority for WHO.”

Meanwhile, the B.1.617.1 sub-lineage has been downgraded to a “variant of interest”, and labelled Kappa. The B.1.617.3 is no longer even considered of interest. “Relatively few reports of this variant have been submitted to date,” the update said.

On May 29, Vietnam Health Minister Nguyen Thanh Long announced that authorities in the Southeast Asian country have detected a new coronavirus variant that is a combination of the strains first identified in India and the UK.

WHO Health Emergencies Programme Technical Lead Maria Van Kerkhove told reporters that this was the B.1.617.2 variant with one additional deletion in the location of the spike protein.