India’s daily new COVID-19 cases have crossed the 8,000-mark for the first time after more than 100 days. However, the cases (moderate to severe) and COVID-19 related hospital admissions continue to be low. The spike in infections has raised some worries about the start of the fourth national COVID-19 wave in India. Epidemiologically speaking, an immediate major national wave in India is improbable. Part of the reason is that the Omicron (B.1.1.529) variant is the only globally circulating variant of concern, as of now. The Omicron sub-lineage BA.2, which caused the third national wave in India, continues to be the dominant variant in the country. Though two new Omicron sub-lineages, BA.4 and BA.5, have been detected globally and reported from India as well, their share is minuscule. Finally, there is no evidence that the BA.4 and BA.5 sub-lineages can cause a major nationwide surge in settings already exposed to BA.2 sub-lineage. Clearly, while the concerns about another national wave are unfounded, the ongoing surge demands for a fresh approach to the COVID-19 pandemic response in India.
Epidemiological triad
Then, a key question is if there is no new variant of concern, why this spike in COVID-19 cases? The answer lies in an age-old concept of epidemiology which explains ‘why’ and ‘how’ a disease spreads in any setting: the ‘epidemiological triad’ of agent, host and environment. Spread of a disease is an outcome of a complex interaction of the agent (or pathogen, in this case SARS-CoV-2 and its variants), host (humans and their immune-biological characteristics) and environment (social and behavioral factors).
