Explainer: What we know about the Indian variant as Covid-19 sweeps South Asia

India has recorded the world's sharpest spike in coronavirus infections this month, with political and financial capitals New Delhi and Mumbai running out of hospital beds, oxygen and medicines.

Scientists are studying what led to an unexpected surge, and particularly whether a variant of the novel coronavirus first detected in India is to blame. The variant, named B.1.617, has been reported in some 17 countries, raising global concern. Here are the basics...