• The coronavirus delta variant first discovered in India has now spread around the world, prompting further waves of infections in countries like the U.K.
• Now, there are increasing signs that mainland Europe is seeing a sharp rise in cases too.
• There have been calls to ban British visitors in order to hep stop the spread of the variant, but experts say it's likely already widespread on the continent.

LONDON — The coronavirus delta variant first discovered in India has now spread around the world, prompting further waves of infections in countries like the U.K.

Now, there are increasing signs that mainland Europe is seeing a sharp rise in cases too.

The EU is certainly worried about the spread of the highly infectious delta variant which evidence suggests is around 60% more transmissible than the alpha variant first found in England, causes more hospitalizations and slightly reduces the efficacy of vaccines.

A number of European countries have introduced further restrictions on visitors from the U.K., but experts believe it's only a matter of time before it takes off in mainland Europe — and there are strong signals it already has.

On Tuesday, French Health Minister Olivier Veran said that the delta variant now represents some 20% of Covid-19 cases in France, up from last week's estimate of it representing 9-10% of cases.

Germany's public health body, the Robert Koch Institute, said this week that the delta variant accounted for around 36% of the cases in the week of June 15 - 20, up 15% from the week before. Lothar Wieler, president of the RKI, also told officials the variant now already represents more than 50% of registered cases in Germany, Deutsche Welle reported Tuesday.

Meanwhile, Italy's national health institute said Friday that cases attributed to Covid variants delta and kappa (a "variant of interest," according to the World Health Organization, that's related to the delta variant) have surged in Italy in the past month, accounting for nearly 17% of total Covid cases.

Spain and Portugal have also reported a rise in delta variant cases as have Poland, Russia, Switzerland and Turkey. In addition, the delta plus variant — a mutation of the delta mutation — has been detected in pockets of Europe too.

Read more: Delta Covid variant has a new mutation called 'delta plus': Here's what you need to know

Too little, too late?

Germany and France are among the countries that have imposed quarantine restrictions on British travelers and Berlin has gone one step further, calling on the EU to take a unified approach when it comes to requiring British travelers who come to the bloc to quarantine.

The move could likely be a case of acting too little, too late, experts note.

"I doubt if European countries with their open economies and more limited border checks, quarantine measures and tracking and tracing will be able to push back delta for long ... especially given that there is extensive local circulation already," Tom Wenseleers, an evolutionary biologist and biostatistician at the Catholic University of Leuven in Belgium, told CNBC Tuesday.

He noted that the actual number of infections in Europe caused by the delta variant could be much higher than estimates currently suggest.

"I estimate that in Portugal 90% of the diagnosed cases now may be delta, but with a strong geographic focus around Lisbon. Many other countries in Europe, like Spain, Germany, Belgium, Luxemburg, Sweden and the Netherlands are not far behind though, with over 50% of all diagnosed cases now also estimated to be delta there," he noted.

The delta variant now accounts for 95% of all new cases sequenced in the U.K. and where Britain goes, it's likely that the U.S. and Europe will follow, experts believe. The European Centre for Disease Prevention and Control said last week that it estimates that by the end of August the delta variant will represent 90% of all Covid viruses circulating in the EU.

Vaccination to the rescue?

Covid vaccination programs could come to the rescue if countries in Europe can deploy shots fast enough. A study by Public Health England in May showed that having both doses of the Covid vaccines developed by AstraZeneca-Oxford University and Pfizer-BioNTech (the vaccines most widely offered in Europe) provide effective protection against the delta variant. Both vaccines were significantly less effective after only one shot, however.

As such, the race is now on in Europe to fully vaccinate millions of people and particularly the young who have been the last in line to receive a Covid shot. Data again from England shows that the young, unvaccinated, over-50s and people who have only had one dose of a Covid vaccine are the most at risk from infection by the delta variant.

KU Leuven's Wenseleers agreed that "vaccinating at maximum speed and asking people in particular risk groups to still exert caution will likely be the main options now" for the EU, "although more intensive border checks and tracking and tracing could help to buy some time until the vaccination campaign has progressed more, which will help to prevent resurgences," he added.

The wider economy

Trouble is already brewing in the EU over the outlook for the summer tourism season and whether to let Brits and others into the region particularly when, for a number of EU countries like Greece and Portugal, tourism is a key component of their economies.

How a potential new wave of delta-variant infections affects the region's wider economy and reopening is also yet to be seen, but economists are keeping a close eye on it.

"The Delta wave is rolling in," Holger Schmieding, chief economist at Berenberg Bank, said in a note Wednesday. "Following the UK with a lag of roughly seven weeks, recorded SARS-CoV-2 infections are apparently starting to edge up in the Eurozone amid major regional variations."

Assessing whether the "new wave" puts Berenberg's above-consensus forecasts for growth in the euro zone and the U.K. at risk (it has forecast GDP growth of 4.7% in the euro zone this year and 7% in the U.K.), Schmieding believed that forecasts would not be impacted to a significant extent.

"Thanks to rapid vaccination progress, we consider it unlikely that medical systems in the U.K. or on the continent will come under such pronounced strains again that new serious restrictions to economic activity will be needed again to keep the medical risks under control … However, we have to watch the risks carefully."