Researchers said that coronavirus super-spreaders were behind the explosion of Covid-19 in India, the country with the most cases after the US. A group of patients that included about 8% of India’s confirmed cases later led to almost two-thirds of its total infections, scientists said in a study published in the journal Science. The research, based on tracing more than 3 million contacts in the southern states of Andhra Pradesh and Tamil Nadu through August 1, is the first major study of transmission in a developing country. While most research on the pandemic has come from China, Europe and North America, cases are now burgeoning in India and other developing countries, according to researchers led by Ramanan Laxminarayan, director of the Center for Disease Dynamics, Economics & Policy who wrote the study. They said barriers to health care are greater in these nations, and the risk of getting severely ill and dying from Covid is higher. In contrast with the super-spreader minority, 71% of confirmed cases whose contacts were traced weren’t found to have spread the virus to anyone. A nationwide serological survey showed that one in 15 Indians have been exposed to the coronavirus. Hospitals in several states are now struggling to secure medical oxygen, needed to assist patients with trouble breathing on their own.