Up to half of all Covid cases in London could be caused by the new Indian variant, according to official figures.
It was last week designated a 'variant of concern' by Public Health England because scientists say it can spread as fast – or even faster – than the dominant Kent strain (B.1.1.7).
But there is no evidence it will cause worse disease or make vaccines less effective, experts say, though it must be monitored in case it turns out to be more dangerous.
In a report last week PHE said it 'may have replaced B.1.1.7 to some extent'. Testing figures suggest that only 50.2 per cent of all positive cases in London were caused by the Kent variant in late April, down from over 90 per cent in March.
The other 49.8 per cent were caused by other strains of the virus. The most common one was the Indian variant (B.1.617). Data showed it made up at least 37.5 per cent of confirmed cases but the exact proportion is unknown because not all samples have been thoroughly analysed.
Professor Christina Pagel, a mathematician at University College London and member of Independent SAGE, said the other half was 'potentially all' the Indian variant. Despite the rapid spread, cases in London remain stable.
The variant has been divided into three types, with type .2 the most common, but only one in five cases of this in London were among returning travellers, showing it is spreading within the city.
In the North West only 16 per cent of people infected with the variant had been out of the country recently, but most other regions saw a third to a half of their cases linked directly to international travel, likely to India.
Dr Deepti Gurdasani, an epidemiologist at Queen Mary University in London, said on Good Morning Britain: 'Cases of this new variant are doubling every week within the UK while other variants are dropping.
'Overall, cases have been dropping, which shows that even with current restrictions in place this variant is growing very, very quickly. In London, 50 per cent of cases now are no longer the so-called Kent variant.'
Professor Christina Pagel, a mathematician at University College London and member of Independent SAGE, produced this graph using PHE data to show that the proportion of Covid cases being caused by the Indian variant type .2 has surged to almost 40 per cent in the most recent data
Public Health England figures reported on May 5, taken from tests up to around April 27, show that fewer than half of cases have been in international travellers in most areas, and that the proportion of cases caused by the Indian variant .2 is rising particularly in London and the North West
The Indian variant has had a meteoric rise since it was first spotted in the UK with cases surging to 790 across all three types, from just 77 a month ago on April 15.
The most cases of type .2, which is the fastest spreading and makes up 520 of the 790, have been in London, with 191.
There were 87 in the North West, 56 in East Anglia and 53 in the South East, with fewer than 50 in all other regions.
In London the variant is confirmed to have made up at least 37.5 per cent of all cases in the week ending April 27. In the North West it was 17.1 per cent.
Scientists are concerned it could be outcompeting the Kent variant, meaning it is becoming more widespread – either because it spreads faster or because it is better at reinfecting people who have been vaccinated or are immune from past infection.
But Professor Sharon Peacock, Cambridge expert and director of COG-UK, which is in charge of analysing new variants, said today: 'There isn't any evidence that this causes more severe disease. There’s just not enough data at the moment.'
Only half of infections run through lab analysis were confirmed to be the Kent strain (green line), compared to over 90 per cent in March. Other variants (purple line) now make up over 49 per cent of cases and the most common of them is the Indian strain – it's even possible it accounts for the full 49.8 per cent
The dominance of the Kent variant (green line) has been weakening in almost all regions, PHE figures show
HALF OF CASES IN SINGAPORE ARE INDIAN VARIANT – BUT IT'S ON TRAVEL GREEN LIST
Half of coronavirus cases in Singapore are being caused by the Indian variant but the country will still be on Britain's travel green list from next Monday.
According to variant tracking website GISAID, 51.9 per cent of analysed samples in the past four weeks were one of the Indian Covid variants, known under the B.1.617 umbrella name.
However, the country has only recorded around 25 cases per day over recent weeks, compared to more than 2,000 per day in the UK. The risk of a traveller contracting the virus there, therefore, is tiny.
In the UK the Indian variants accounted for five per cent of infections over the same time period, while in India it was 46 per cent.
International travel will be legal from next Monday, May 17, but there will still be tough testing and quarantine restrictions for most destinations, as well as difficulties getting into countries still battling large outbreaks.
One of scientists' biggest concerns about the Indian variant is that it has evolved – or will evolve further – in a way that makes vaccine immunity less effective against it.
Early tests by a lab run by Professor Ravi Gupta at the University of Cambridge suggested that the original version of the Indian variant (type .1) saw a slight dip in effectiveness of immunity, but not as bad as with the South African strain.
It suggested that levels of useful antibodies – virus-fighting proteins made by the immune system – were about six times lower than with the Wuhan variant. But for the South African strain they were 10 times lower in similar tests, the team said.
Professor Gupta said: 'Although at population level, with good vaccine coverage the mortality rate and severity will be very low in the post-vaccination era, there are people out there susceptible to this virus who cant be vaccinated.
'That fraction of people is larger than one may think because it includes people with diabetes and underlying conditions.
'Variants may increase the margin of getting around those defences and, if those defences are at lower levels, it increases the risk of severe illness.'
The Government revealed last week that scientists now think the variant — linked to an explosion of cases in India — is 'at least' as infectious as the current dominant Kent strain.
Cases have more than doubled in a week and there are clear hotspots in Bolton and London.
Health officials are confident vaccines currently being used should still work against the variant but are carrying out urgent tests to be certain.
Scientists have grouped the Indian variant into three separate sub-strains, with type 2 quickly spreading in the UK. It has been found in schools, care homes and places of worship, it was reported.
The other two are genetically similar strains — B1617.1 and B1617.3 — and aren't currently considered variants of concern. But PHE said their status will be kept 'under constant review'.
Despite being more infectious, health chiefs don't believe the variant is deadlier than original coronavirus strains.
The move to make the Indian variant one 'of concern' means officials can now put in place tougher measures to contain the strain, including ordering door-to-door tests and boosting contact tracing. All residents living in areas where the variant is spreading in the community will be asked to get a test, even if they don't have symptoms.
The Department of Health announced it would start surge testing in Bolton in the BL3 postcode and has asked residents to book a test online or on the phone so they can go for one at a site or have one delivered to them at home. Surge testing in London has not yet been announced.
Prime Minister Boris Johnson said that tracking of the Indian variant will be 'absolutely ruthless'.
While celebrating local election victories last week, Mr Johnson told reporters: 'What we're doing there is making sure that we are absolutely ruthless in the surge testing, in the door-to-door tracking of any contacts.
'At the moment we're looking carefully at the way the Indian variant seems to function, we don't see any evidence that it is resistant to the vaccines or in any way more dangerous.'
But one expert warned the Prime Minister's roadmap out of lockdown might be delayed because of outbreaks of the variant.
Dr Duncan Robinson, policy and strategy analytics academic at Loughborough University, said a 'political decision' may be taken to slow down easing restrictions because the strain could disproportionately affect areas where there are outbreaks.
WHAT DO WE KNOW ABOUT THE INDIA VARIANTS?
When and where was it discovered?
The variant was first reported by the Indian government in February 2021.
But the first cases appear to date back to October 2020.
Its presence in the UK was first announced by Public Health England on April 15. There have since been at least 400 cases spotted in genetic lab testing.
What mutations does it have?
It has 13 mutations that separate it from the original Covid virus that emerged in China — but the two main ones are named E484Q and L452R.
Scientists suspect these two alterations can help it to transmit faster and to get past immune cells made in response to older variants.
PHE officials said it has split into three distinct virus types, with types 1 and 3 both having the E484Q mutation but type 2 missing the change, despite having all the other hallmarks of the variant.
Is it more infectious and can it evade vaccines?
The L452R mutation is also found on the Californian variant (B.1.429), even though the two evolved independently. It is thought to make the American strain 20 per cent more infectious than the original Wuhan version – even with the extra 20 per cent it is likely slower than the Kent variant.
The E484Q mutation is very similar to the one found in the South African and Brazil variants known as E484K, which can help the virus evade antibodies.
The South African variant is thought to make vaccines about 30 per cent less effective at stopping infections, but it's not clear what effect it has on severe illness.
Professor Sharon Peacock, of PHE, claimed there was 'limited' evidence of E484Q's effect on immunity and vaccines. Lab studies have suggested it may be able to escape some antibodies, but to what degree remains uncertain.
Early research suggests both the AstraZeneca vaccine, known as Covishield in India, and the Pfizer jab, still work against the variant, as well as India's own jab, Covaxin. A paper published by SAGE last week suggested two doses of the Pfizer vaccine is good enough to protect against all known variants.
How deadly is it?
Scientists still don't know for sure. But they are fairly certain it won't be more deadly than the current variants in circulation in Britain.
This is because there is no evolutionary benefit to Covid becoming more deadly. The virus's sole goal is to spread as much as it can, so it needs people to be alive and mix with others for as long as possible to achieve this.
And, if other variants are anything to go by, the Indian strain should not be more lethal.
There is still no conclusive evidence to show dominant versions like the Kent and South African variants are more deadly than the original Covid strain - even though they are highly transmissible.
Doctors in India claim there has been a sudden spike in Covid admissions among people under 45, who have traditionally been less vulnerable to the disease.
There have been anecdotal reports from medics that young people make up two third of new patients in Delhi. In the southern IT hub of Bangalore, under-40s made up 58 percent of infections in early April, up from 46 percent last year.
There is still no proof younger people are more badly affected by the new strain.
Should we be worried?
Scientists are unsure exactly how transmissible or vaccine-resistant the Indian variant is because it hasn't been studied thoroughly.
The fact it appears to have increased infectivity should not pose an immediate threat to the UK's situation because the current dominant Kent version appears equally or more transmissible.
It will take a variant far more infectious strain than that to knock it off the top spot.
However, if the Indian version proves to be effective at slipping past vaccine-gained immunity, then its prevalence could rise in Britain as the immunisation programme squashes the Kent variant.
Scientists believe this variant can spread more quickly than two other related variants seen in India.
It is thought to be at least as transmissible as the variant detected in Kent last year, known as B117, which is now dominant in the UK.
Dr Susan Hopkins, Covid-19 strategic response director at PHE, said: 'We are monitoring all of these variants extremely closely and have taken the decision to classify this as a variant of concern because the indications are that this VOC-21APR-02 is a more transmissible variant.'
PHE said there is currently 'insufficient evidence' to indicate that any of the variants recently detected in India cause more severe disease or make the vaccines available any less effective.
How many cases have been detected in the UK?
According to data by PHE released on Friday, there are, at present, 520 confirmed cases of the B.1.617.2 variant in the UK, from 202 over the last week.
The cases are spread across the country, with the majority in two areas – the North West, mainly in Bolton, and London.
PHE said around half of these cases are related to travel or contact with a traveller.
PHE health protection teams are working with local authorities, public health officials and NHS Test and Trace to detect cases and limit onward spread.
Surge testing is expected to be deployed where there is evidence of community transmission.
Is B16172 variant driving the second wave in India?
India reported 412,262 new Covid-19 cases and 3,980 Covid-19-related deaths on Thursday — both new single-day records.
In the past 30 days, the country has recorded 8.3million cases.
However, it remains unclear whether the new coronavirus variants are driving the second wave.
Experts say large gatherings, and lack of preventive measures such as mask-wearing or social distancing, are playing a key role in the spread of the virus.
Although India has the world's biggest vaccine making capacity, the country has partially or fully immunised less than 10 per cent of its 1.35billion people.