The bewildering speed with which coronavirus has overwhelmed India’s health systems has sparked global alarm over the viral variant that emerged in the subcontinent.

The B.1.617 variant has been blamed by some for the surge in infections in India, which recorded more than 350,000 confirmed cases on Monday alone, a world record for one county in a single day. Health experts believed the true figure was likely to be much higher.

But scientists have urged against leaping to conclusions about the extent to which the variant alone is responsible for the dizzying rise in cases in the past few weeks, which caused 2,800 confirmed deaths in India on Monday alone. They said there was little hard evidence about the virulence and transmissibility of the Indian variant and point to other possible factors.