A variant of Covid-19 first found in India has become the latest to attract widespread concern over fears it could spread more easily or even bypass vaccines.
The focus on the B1617 variant follows a massive surge of virus cases in India, along with evidence the variant is becoming established in England.
The sci fi-like description of it as a “double mutant” variant – because it has two key mutations found in other problematic variants – has caused particular alarm.
From a small base, B1617 cases in England are doubling weekly, with the latest update recording 103 cases.
This has prompted calls for India to be placed on the "red list" of countries requiring mandatory hotel quarantine for incoming travellers to the UK. On Monday, prime minister Boris Johnson cancelled a trip to India planned for next week.
Viruses change all the time, so new variants are to be expected. Mutations can result in the virus becoming more transmissible; increasing the severity of disease; and/or affecting the effectiveness of vaccines and treatments.
Some mutations, or combinations of mutations, can give the virus a selective advantage. When these variants increase the risk to human health, they are considered to be variants of concern (VOCs).
B117, or the UK variant, is the best-known one here after it became dominant within a matter of weeks over Christmas. Because it was more transmissible, many more people fell ill.
The World Health Organisation has categorised two other VOCs – B1351, the South African variant, and P1, from Brazil.
Thanks to control measures and the superior fitness of the UK variant, only small numbers of these variants have been found here to date.
B1617 has come to notice too recently to be classified a VOC; we don’t know yet whether it is more transmissible or better at vaccine-escape. But the fact that it started during lockdown and has spread even with widespread vaccination of the English population has attracted attention.
Public Health England has said there is currently no evidence to suggest that disease from the newly-identified variant is more serious than from previous ones, nor is there current evidence to suggest vaccines are less likely to work against it.
Trinity College Dublin virologist Prof Kim Roberts says it has some "interesting" mutations but also lacks some mutations one might expected to see in a VOC. Despite the attention it has garnered, the variant has been sequenced only 567 times worldwide, she points out.
“At the moment there is very little information, so we’ll have to wait and see, and stay vigilant.”
It isn’t known for certain that the new mutation is driving the surge of infections in India, where 200,000 new cases a day are being recorded. This is because under 1 per cent of cases are sequenced to determine what variant is involved.
Evidence of the harm that the variant could inflict is more likely to come from the UK, which leads the way in sequencing and analysis.
"But by the time we do, B1617 is likely to be quite widespread and it might be too late to contain it," says Prof Christina Pagel, mathematician and head of the clinical operational research unit at University College London. The variant "could" become dominant in England by the end of June, she has tweeted.
This sudden assumption of dominance is what happened with the UK variant in Ireland after Christmas, largely through the importation of cases.
Many other scientists internationally, while watchful, are more relaxed about the threat posed by the Indian variant. It has been around since last year without making big inroads, they point out. Specifically, it has struggled to compete against the UK variant.
Prof Roberts says most of the cases reported in England are travel-related and community transmission does not appear to be a factor.
She says we need to be able to respond quickly to changes in transmission dynamics, including surges in other countries, by adding to the number of destinations requiring mandatory hotel quarantine.
It remains the fact that all of the main vaccines provide comprehensive protection against serious illness and death from the virus. Future versions of the vaccines will be tweaked to improve protection against known variants, but this will be a continuous battle as the virus continues to mutate.