The 'epidemiological triad' of factors--the agent, the host and the environment--must all be studied, said Giridhar Babu, an epidemiologist with the Public Health Foundation of India. "The agent is the virus which is definitely changing and scientists are still figuring out things about the variants by genome sequencing," he said, "As hosts, whether all of us have been practicing Covid-19 precautions, and getting vaccinated, will explain why there's a rise in numbers. And as for the environment, it is everything happening around us, such as whether the government is allowing cinemas, public transport and events that can allow the spread of the virus."