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India is in the grip of a brutal second wave of Covid-19, setting global records for the numbers of cases and deaths each day.
On Monday, it recorded 352,991 new cases and its total number of infections since the start of the pandemic is now more than 17 million.
Another 2,812 deaths were confirmed, pushing India’s overall tally of Covid-19 fatalities to 195,123.
India's population is currently estimated at about 1.4 billion people.
The surge is believed to be fuelled by a mixture of complacency and a new Covid-19 variant, which doctors say is spreading faster than previous strains.
The world stepped in with offers to help, as countries suspended travel to India to stem the spread of the new variant.
But what about the strain makes it spread faster? And are vaccines effective against it?
The National explains everything we know about the strain.
How did the situation become so bad in India?
Some people in India believed the country was reaching the end of its battle against Covid-19 in March.
Cases declined from a peak in September to comparatively low levels in February.
Antibody studies suggested there should have been a degree of immunity among the population, particularly in big cities such as New Delhi, where 56 per cent of people tested positive for antibodies, according to a study released in early February.
That made the scale of the second wave, which has been referred to "a wall" because of its severity, all the more surprising, even to scientists.
What is behind India's new explosive Covid-19 surge?
Could the surge in cases be down to the new ‘Indian variant’?
It could certainly be playing a role.
But Ramanan Laxminarayan of the Centre for Disease Dynamics, Economics & Policy said the surge could be explained by changes in behaviour alone.
He told the BBC that events such as religious gatherings, election rallies, weddings and the opening of cinemas at full capacity could have led to the surge.
In some areas the UK strain is dominant. But the Indian variant, or B1617, appears to be spreading fast.
In the state of Maharashtra, where Mumbai is located, the strain exploded and now accounts for about 50 per cent of the samples tested. It is spreading faster than the UK strain, experts said.
How many mutations does B1617 have? And what are their likely effects?
The strain has 15 mutations from the original virus.
But five of the mutations are on the spike protein of the virus, which the virus uses to enter our cells.
Two mutations are of particular concern. They are known as known as E484Q and L452R and it is the first time they evolved together in a single variant, hence the "double mutant" tag.
Speaking on a BBC science podcast, Ravi Gupta, professor of Clinical Microbiology at the Cambridge Institute for Therapeutic Immunology and Infectious Diseases, said that more information was needed about the effect of the combined mutations.
But they are both known to separately help the virus evade antibodies, to an extent.
“The 484 mutation is seen in the variant that emerged in Brazil [and] the one that emerged in South Africa. We have also seen mutations there in the B117, which has developed this in a number of areas, including in the US and the UK,” Prof Gupta said.
“So it is something the virus does like to do.
“It has biological significance and the significance is that it does stop some of our antibodies that we make from vaccination or natural infection. It blocks the antibodies. It is an escape mechanism for the virus to get around our defences.”
The L452R mutation was found in a variant first detected in California. It was shown to also "confer a degree of escape to antibodies", Prof Gupta said.
Doctors said there appeared to be a larger proportion of asymptomatic infections, as well as patients with "non-standard symptoms". Patients also seem to be younger, compared with the first wave.
Do vaccines protect people against the strain?
Because the variant was only recently detected, research is still in an early phase.
But scientists said vaccines should offer at least partial protection against the strain.
Prof Gupta said on Twitter that it was “likely vaccines will protect against severe illness and death but not against infection in those [people] with poorer immune responses".
The Indian Council of Medical Research said the vaccine Covaxin appeared to "effectively neutralise" the strain.
Bharat Biotech, an Indian biotechnology company with its headquarters in Hyderabad, said it had a stockpile of 20 million doses of Covaxin and planned to make 700 million doses by the end of 2021.
Covaxin was introduced in India after it was cleared for emergency use among millions of vulnerable people while clinical trials were still under way.
Both the manufacturer and medicine regulator defended the vaccine, saying it was "safe and provides a robust immune response".
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