Delta variant triggers dangerous new phase in the pandemic

When the coronavirus variant now called Delta first appeared in December 2020, in the Indian state of Maharashtra, it did not seem all that remarkable. But when it descended on New Delhi a few months later, its impact was devastating, with almost 30,000 cases reported daily in late April. “Suddenly … it is dominant and completely sweeps away Alpha,” which until then was most prevalent in the city, says Anurag Agrawal, who leads the Institute of Genomics and Integrative Biology in New Delhi.

New Delhi seemed unlikely to suffer a big new outbreak because so many of its residents had already been infected or vaccinated, Agrawal says. But those protections seemed to barely slow Delta, which is more transmissible and may evade immunity, he says: “It went from a 10-foot wall around the city to a 2-foot wall you could just walk over.”

From New Delhi, the variant has quickly spread, and it now looks set to sweep the globe in what could be a devastating new wave. In the United Kingdom, Delta already makes up more than 90% of all infections; it has driven COVID-19 case numbers up again after a dramatic decline and led the government last week to postpone the final stage of its reopening plan. A Delta-driven resurgence in Lisbon prompted the Portuguese government to enact a 3-day travel ban between the city and the rest of the country. The variant may account for 90% of all COVID-19 cases in the European Union by the end of August, Andrea Ammon, the head of the European Centre for Disease Prevention and Control, warned today. “It is very likely that the Delta variant will circulate extensively during the summer, particularly among younger individuals that are not targeted for vaccination," she said. "This could cause a risk for the more vulnerable individuals to be infected and experience severe illness and death if they are not fully vaccinated.“

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