India has classified a new variant of the coronavirus first identified in Europe as a "variant of concern", but it's too early to tell whether it poses a significant threat.
India's health ministry says studies showed that the so-called Delta plus variant - also known as AY.1 - spreads more easily, binds more easily to lung cells and is potentially resistant to monoclonal antibody therapy, a potent intravenous infusion of antibodies to neutralise the virus.
The variant is related to the Delta, an existing variant of concern, which was first identified in India last year and is thought to have driven the deadly second wave of infections this summer in India.
The health ministry says the Delta plus variant, first found in India in April, has been detected in around 40 samples from six districts in three states - Maharashtra, Kerala and Madhya Pradesh. At least 16 of these samples were found in Maharashtra, one of the states hardest hit by the pandemic.
Delta plus has also been found in nine other countries - USA, UK, Portugal, Switzerland, Japan, Poland, Nepal, Russia and China - compared to the original highly contagious Delta strain, which has now spread to 80 countries.
Viruses mutate all the time and most changes are inconsequential. Some even harm the virus. But others can make the disease more infectious or threatening - and these mutations tend to dominate.
A mutation is elevated from a "variant of interest" to a "variant of concern" (VOC) when it shows evidence of fulfilling at least one of several criteria, including easy transmission, more severe illness, reduced neutralisation by antibodies or reduced effectiveness of treatment and vaccines.
But leading virologists have questioned the labelling of Delta plus as a variant of concern, saying there was no data yet to prove that the variant was more infectious or led to more severe disease compared to other variants.
"There is no data yet to support the variant of concern claim," said Dr Gagandeep Kang, a virologist and the first Indian woman to be elected Fellow of the Royal Society of London.
"You need biological and clinical information in order to consider whether it is truly a variant of concern."
This means India needs more data to determine whether the variant is neutralised by antibodies generated by available vaccines or infection by another variant of the coronavirus.
Also, extensive data is needed about the increase in transmissibility, diagnostic failures - routine tests not picking up the variant - and whether the variant is causing more severe disease.
"You need to study a few hundred patients who are sick with this condition and variant and find out whether they are at greater risk of greater disease than the ancestral variant," Dr Kang said.
The Delta plus variant contains an additional mutation called K417N on the coronavirus spike, which has been found in the Beta and Gamma variants, first found in South Africa and Brazil respectively (Beta was linked to increased hospitalisation and deaths during South Africa's first wave of infections, while Gamma was estimated to be highly transmissible).
Even with 166 examples of Delta plus shared on GISAID, a global open sharing database, "we don't have much reason to believe this is any more dangerous than the original Delta," according to Dr Jeremy Kamil, a virologist at Louisiana State University Health Sciences Center in Shreveport.
"Delta plus might have a slight advantage at infecting and spreading between people who were previously infected earlier during the pandemic or who have weak or incomplete vaccine immunity," Dr Kamil told me.
"I would keep calm. I don't think India or anyone else in the world has released or accumulated enough data to distinguish the risk from the so-called Delta plus as being more dangerous or concerning than the original Delta variant."
Dr Anurag Agarwal, director of the Delhi-based CSIR-Institute of Genomics and Integrative Biology (IGIB), one of the 28 Indian labs involved in genome sequencing, said "all lineages of the Delta variant are variants of concern", so there was nothing unusual in labelling Delta plus as such.
"We do not have any indicators as of now to show that Delta plus should be causing any public health worry or panic. We are not seeing anything worrisome yet. We are tracking it carefully, and strengthening all public health measures," he said.
Dr Kamil said the government in India "would rather over-react now than seem flat-footed later, as was the case with the Delta variant".
Most scientists say India dropped the ball on sequencing enough samples for the variant which had fuelled a massive second surge in Covid infections in India in April and May.
"I am not overly worried. But it's fair to keep an eye on the variant."