In Britain, the Delta variant now makes up the majority of cases in the country, even though the British vaccination campaign has been faster than in Germany, prompting a delay in the easing of lockdown rules.

The variant is more transmissible and is said to be more severe, initial data has suggested.

In Germany, the proportion of cases of the Delta variant almost doubled within the first week of June to 6 per cent, according to figures by the Robert Koch Institute (RKI) for disease control.

However, the absolute number of cases detected is falling.

The situation in Germany could stay relatively stable for the time being, said Drosten, in his podcast “Coronavirus Update,” which is produced in conjunction with broadcaster NDR.

He said it was likely that fewer individuals infected with the variant had entered the country, citing people travelling directly from India, where the Delta variant first emerged.

The RKI is due to provide its latest figures on Wednesday.

Drosten said it would be a “very bad sign” if that data showed the proportion of cases of the Delta variant were doubling every week.

Since the figures provided by the RKI reflect the situation from around two weeks earlier, it would be impossible to correct the trend retroactively, Drosten said, adding that there was a risk of the figures doubling again the following week.

“If that were the case, then we would have to be prepared for other developments with the Delta variant resembling those in Britain,” Drosten said.

He said the proportion of cases of the Delta variant in Germany was a key indicator to follow.

Rather than making predictions about the summer, it’s important to watch what happens,” he said.

“I think we’ll be smarter a week from today,” Drosten said.