Delta plus variant: The coronavirus strain that has Spanish experts on alert

The experts on the front line of the battle against Covid-19 are not dropping their guard. Despite the fact that more than 78% of the population of Spain is fully vaccinated, and the 14-day incidence of cases per 100,000 inhabitants is currently at 49, work continues to monitor possible threats that could see the pandemic spiral out of control once more.

The latest of these dangers is a new mutation of the delta strain that is slightly more transmissible, and that has been dubbed delta plus. Epidemiologists and microbiologists are keeping a close eye on this variant, with around 30 cases confirmed in Spain so far. While it has been detected in a number of Spanish regions, the experts say that it does not appear more aggressive than other strains and they are calling for calm. It is not known, for now, as to whether it evades the protection offered by Covid-19 vaccines, but the same experts say that this is unlikely.

The technical name for this delta sub-variant is AY.4.2, and it was detected for the first time in the United Kingdom over the summer, according to the European Center for Disease Prevention and Control (ECDC). It differs from the delta variant – which is currently the predominant strain in Europe – due to its five mutations, and it can be 10 to 15% more transmissible, according to the experts consulted by EL PAÍS. When the delta variant was first detected in India, it was found to be 50% more infectious than its predecessor, the alpha variant – which in turn was 50% more infectious than that which gave rise to the pandemic in Wuhan, China.

The ECDC is keeping delta plus on its list of variants that it is monitoring – i.e. those which have similar properties to so-called “variants of concern.” These properties include a significant impact on transmissibility, severity or immunity. The testing that has so far been carried out is either insufficient or has not been properly evaluated by the ECDC.

The vice president of the Spanish Virology Society, Juan García Costa, is calling for caution when it comes to the data arriving from the United Kingdom. “There is no evidence that delta plus could occupy the ecological niche of delta,” he explains. “But given that it is a subvariant, the effect will not be very different. We don’t know if it will dominate, disappear or if both will live side-by-side.”

In the UK, this cousin of the delta variant accounted for around 6% of cases detected in the first week of October, according to the latest report from the UK Health Security Agency. But for now, the health authority is ruling out that it might be more aggressive, stating in the report that it does not appear to be causing more serious illness or evading the effect of the vaccines.

We need to see how it evolves, be vigilant in case it spreads or not, and see if it is more or less resistant to the vaccine

Tomàs Pumarola, head of microbiology at the Vall d’Hebron hospital in Barcelona

The international database for human virus sequencing, GISAID, has reported the presence of this strain in 30 or so countries. In Spain, it has been confirmed in the regions of Catalonia (five cases), Navarre (one), Madrid (four), Andalusia (one), Extremadura (three), Castilla-La Mancha (three) and Castilla y León (four). But in Gisaid, where microbiologists report sequenced samples, there are as many as 35 confirmed cases of delta plus that originated in Spain, according to the latest Health Ministry report on variants.

Aside from these conflicting figures, Tomàs Pumarola, the head of microbiology at the Vall d’Hebron hospital in Barcelona, is calling for calm. “It doesn’t matter how many cases there are,” he says. “The important thing is that this variant is circulating in Spain and continues to be sporadic. We need to see how it evolves, be vigilant in case it spreads or not, and see if it is more or less resistant to the vaccine. But it doesn’t appear to be more virulent.”

Elena Vanessa Martínez, the president of the Spanish Epidemiology Society, is also seeking to calm nerves about this sub-variant – at least, for now. “This has happened with other sub-variants of delta, they have risen and then they have fallen once more,” she explains. “It seems to be more transmissible, but we will have to see about that. We have to closely follow all of these viruses.”

So far more than a hundred variants of the delta strain have been detected. But Jesús Rodríguez Baño, the head of infectious diseases at the Virgen de la Macarena Hospital in Seville, insists that “the probability that [delta plus] evades the vaccines is low.” He adds that “we would do well to remain vigilant, but there is no need to obsess over every single variant.”

The experts are also ruling out that the rise in infections currently being seen in the UK (925 cases per 100,000 inhabitants over the last 14 days) is closely linked to the spread of delta plus. “The numbers don’t add up,” says Pumarola. “England has raised the alarm at a time when infections with this sub-variant are very low and do not justify the high incidence right now. This sub-variant only represents 6% of new infections. I believe it’s more a question of the fact that they have returned to complete normality: they are seeing a lot of infections and there is also an impact on their hospitals,” he explains.

Martínez agrees, and points to the fact that in England masks are no longer legally required in any settings (they are still necessary in certain indoor situations in Wales, Scotland and Northern Ireland), and that just 67% of the population of the UK as a whole is fully vaccinated – much lower than other countries such as Spain.

Toni Trilla, the chief epidemiologist at the Hospital Clínic in Barcelona, also puts the high circulation of the virus in the UK down to a series of reasons, not just to delta plus. “It’s a cocktail of relaxation of protection measures based on political and economic criteria, with inferior vaccination conditions, that has made the situation in the United Kingdom different to Spain and more complicated.”

We would do well to remain vigilant, but there is no need to obsess over every single variant

Jesús Rodríguez Baño, head of infectious diseases at the Virgen de la Macarena Hospital

As such, when it comes to extrapolating what is happening in the United Kingdom in general and with the delta plus variant in particular, the experts point to the need to contextualize the situation. Protection measures in Spain are not as lax as they are in the UK, and in any case, the epidemiological situation is also different to the one when other variants, such as delta or alpha, began to circulate: now, a large percentage of the population is vaccinated.

“Months have passed since it was detected in the United Kingdom until now, and it is just 6% of new cases,” Trilla explains. “It has not spread at the same speed as delta. Maybe it doesn’t have the same capacity to dominate and is, what’s more, finding more vaccinated people.” Pumarola points out that the alpha variant did not begin to spread rapidly until it reached 10% of new infections, meaning that “it is possible that it needs a minimum presence to spread faster,” Trilla adds.

The microbiologist from Vall d’Hebron also states that we will have to get used to the appearance of these new variants. “Since delta arrived, what we are seeing is that it is diversifying given the immunological pressure, because it is finding people who are vaccinated or already infected.” The microbiologist argues that, while the end of the pandemic is near, this coronavirus “is here to stay.” As more people are vaccinated, he continues, “the virus will change more quickly and will force us to reformulate the vaccines, which were created with the variant from Wuhan. Now we are protected against serious disease, but not so much against the infection and the virus is circulating more freely. A variant will appear that will force us to re-vaccinate ourselves,” the specialist insists.