- More contagious - The Delta variant of Sars-CoV-2 was first detected in India where it began circulating around April.
It is now present to varying degrees in at least 85 countries according to the WHO. In Europe, Delta initially gained a foothold in the United Kingdom, where it quickly outpaced the previous variant of concern Alpha, and now comprises 95 percent of all sequenced cases in England.
Delta is thought to be some 40 to 60 percent more contagious than Alpha, which itself is more contagious than the strain responsible for the first wave of Covid-19.
The pattern has repeated elsewhere. In the United States last week 35 percent of positive tests that were sequenced were identified as the Delta variant, up from about 10