Government officials are still scrambling to track down the mystery case of the worrying Brazil strain – but it’s not the only Covid variant being monitored carefully.
Here’s where things stand with all of the “variants of concern”.
The number of confirmed and probable cases for the Kent variant stands at 105,428. This strain was first detected in September and its spread led to the cancellation of a planned relaxation of measures at Christmas and the second national lockdown.
It is now thought to be the dominant variant in the UK.
Analysis of the variant suggests it is up to 70% more transmissible than the previous strain that was dominant in the UK.
South Africa variant
There were, as of Monday, 288 cases of the South Africa variant in the UK. That’s the strain that sparked “surge testing” at the beginning of February when 11 cases were recorded in people who hadn’t travelled to the country.
At that time there was a total of 105 cases of the highly-transmissible variant, which was first identified in the UK in December. Some 80,000 people were targeted with the door-to-door and mobile testing initially, with more areas added when cases were identified.
As well as helping slow the transmission of the variant, the surge testing helps experts learn more about the variant by sequencing genomic data.
That the number of cases remains at a relatively modest 288 suggests the surge testing policy is managing to contain the spread of the virus.
Another variant of concern is a mutation of the Kent strain first found in Bristol last month. It carries the E484K mutation, which experts suggest may be better at evading the human immune response, but since the first 11 cases were announced on February 2 and surge testing was rolled out, only 21 more have been recorded and the total stands at 32.
The location of the unidentified person who tested positive for the variant first seen in Manaus has been narrowed down to 379 households in the south-east of England.
The government announced on Sunday that the Brazil variant had been identified in the UK. Public Health England (PHE) confirmed six cases – three in England and three in Scotland.
Two cases were confirmed in South Gloucestershire, but the third English case is the missing person. PHE says the person did not complete their test registration card fully and their contact details were therefore not known.
The three Scottish residents tested positive after flying into Aberdeen from Brazil, via Paris and London.
Though low in numbers, there is concern about the Brazil variant, with research from Manaus suggesting between 25% and 61% of people who have previously had Covid are susceptible to reinfection from the strain, which is also up to twice as transmissible as earlier strains.
However, British scientists have cautioned that the study cannot be used to predict what might happen in the UK and say it does not suggest that vaccines will not work against it.
Experts do not so far believe that the Manaus variant is more transmissible than the Kent variant, which in itself is more transmissible than the original pandemic strain.
Health Secretary Matt Hancock told MPs on Tuesday that current vaccines had not been studied against the Manaus variant, which he said has caused “significant challenges” in Brazil.
Professor Ester Sabino, from the University of Sao Paulo, said: “You need many introductions [of a virus] to start an epidemic.
“Six is very few. I would say if you take care and do contact tracing, this is going to decrease.”
Dr Thomas Mellan, from Imperial College, London, said researchers have found a somewhat increased risk of death with the strain in Manaus, but this was in a city with “substantial healthcare failure” such as a lack of oxygen.
Variants under investigation
None of the remaining strains, classed as “variants under investigation”, have registered over 100 cases.
There are 42 cases of another Brazil variant, first identified in the UK in November.
A strain with similar mutations to the Bristol variant and which was seen in areas around Liverpool last month has 58 confirmed cases.
And last month scientists identified another new variant of coronavirus known as B.1.525, which appears similar to the South Africa variant.
Public Health England (PHE) has said there is no evidence it is more transmissible or causes severe disease. As of February 16, 38 cases had been identified in the UK. There are now 67 confirmed cases.