Health officials announced on Sunday that one in three Covid-19 infections in the UAE stemmed from the highly contagious Delta variant.
Delta is the name given to the variant first detected last October in India.
It prompted a devastating surge in case numbers in the country and is also responsible for more than 90 per cent of new infections in the UK, according to Public Health England.
A potentially more transmissible mutation of Delta was recently discovered in India, identified as Delta Plus.
The World Health Organisation says the mutation could prove to be more deadly as time goes on.
But what is the new strain and how does it differ from Delta, already described a variant of concern by the WHO.
What is the Delta variant?
The WHO has given names to coronavirus variations in an effort to remove any stigma associated with the countries where they were first detected.
Greek letters have been assigned to the strains in the order they were designated variants of concern, starting at Alpha for the strain first detected in the UK last year.
The Delta variant was first recorded in India and is 60 per cent more infectious than the Alpha strain, according to the British authorities.
Doctors have said it affects patients differently to the original coronavirus.
Common symptoms include fever, headaches and a runny nose. At first, it appears more like a head cold, with a sore throat and sneezing.
Delta does not seem to affect patients' sense of smell.
If you have any symptoms, the authorities recommend regular testing for Covid-19, to prevent the disease spreading among the community.
What is the Delta Plus variant?
Delta Plus is a mutated version of Delta, which is also known as B.1.617.2.
It has been named 'Plus' locally, but its official name is Delta-AY.1.
The Delta strain is characterised by the K417N mutation in the spike protein of the Sars-CoV-2 virus that causes the Covid-19 disease.
This mutation is also present in the Beta variant, first found in South Africa.
There are concerns the variant could be 50 per cent more transmissible than other strains, but epidemiologists have said more sequencing needs to be done.
“There is speculation regarding higher transmissibility and infectivity of the Delta Plus variant, but there is no definitive data to support this,” said Binay Panda, a professor of biotechnology at Jawaharlal Nehru University in New Delhi.
Delta mutation 'becoming more deadly'
Dr Soumya Swaminathan, the WHO's chief scientist, admitted there were concerns about the new strain.
"The reason it's been called Plus is because it has another mutation, which is also seen in the Beta and Gamma variants, which could potentially also impact the antibody killing off the virus," she said.
"So there's a bit of concern that this strain may be becoming even more deadly, because it's now going to become resistant to drugs and vaccines.
"The good thing is that there are still very few cases that have been described globally, so we can track what is happening.
"We need more studies to see whether this Delta variant with this additional mutation has any other properties. We are tracking that and are collecting that information."
Where is Delta Plus spreading?
The earliest case of Delta Plus was in India from a sample taken on April 5.
The Indian authorities said there have now been 50 cases and three deaths across three states, including Maharashtra, Tamil Nadu and Madhya Pradesh. The cases were found by sequencing 45,000 samples.
As a consequence, India's richest state, Maharashtra, has tightened lockdown restrictions.
The Indian Health Ministry said Delta Plus showed increased transmissibility and advised states to increase testing.
The spread was mostly very localised, said Balram Bhargava, director general of the Indian Council of Medical Research.
However, at least 12 other countries have reported cases of Delta Plus, including the US, UK, Japan, Russia and China, he said.
Portugal's Health Minister Marta Temido, said they had detected 24 cases on June 23.
Britain said its first five cases were sequenced on April 26 and they were contacts of individuals who had travelled from, or transited through, Nepal and Turkey.
Why is Delta Plus a cause for concern?
As with all variants, the concern is that they could be more transmissible or more deadly.
Immunologists also worry about vaccines' effectiveness against new variants.
Shahid Jameel, a senior Indian virologist, said K417N was known to reduce the effectiveness of a cocktail of therapeutic monoclonal antibodies, medicines like the newly available Sotrovimab, which help the body fight Covid-19 infections.
Studies are taking place to test the effectiveness of India's vaccines against the Delta Plus variant, including AstraZeneca’s Covishield and Bharat Biotech International's Covaxin.
"We should have the results in about 7 to 10 days' time whether the vaccine is working against the Delta Plus," Mr Bhargava said.
The WHO said it was tracking the variant.
"For the moment, this variant does not seem to be common, currently accounting for only a small fraction of the Delta sequences. Delta and other circulating variants of concern remain a higher public health risk as they have demonstrated increases in transmission," it said.