Almost half of Karnataka’s population may have been infected by Covid-19 by August, nearly 100 times more than the officially reported figures during that time, a seroprevalence study has estimated.
The survey, carried out by the Mumbai-based IDFC Institute, found that at least 44.1 per cent of the population in rural areas of Karnataka and 53.8 per cent in urban areas were exposed to the coronavirus, and, as a result, developed antibodies to the infection.
The sero survey used data collected from a representative sample of households in 20 districts of the state from mid-June through August. The state has a population of roughly 6.4 crore.
Adjusted seroprevalence across Karnataka implies—based on the government mid-year 2020 population estimates—that approximately 3.15 crore residents have been infected. This is 96.4 times the 327,076 publicly reported cases as of August 29.
Sero studies conducted in a random population are essential for measuring the spread of the Covid-19 pandemic. Researchers from the IDFC Institute carried out the Karnataka study in collaboration with the Centre for Monitoring Indian Economy. The study, funded by ACT Grants (India), was led by Professor Manoj Mohanan from Duke University, Professor Anup Malani from Chicago University, and Anu Acharya from Mapmygenome along with Kaushik Krishnan from the Center for Monitoring Indian Economy.
The presence of antibodies in the blood typically suggests that people infected with a virus would gain immunity for some period of time. The new study, Prevalence of COVID-19 In Rural Versus Urban Areas in a Low-Income Country: Findings from a State-Wide Study in Karnataka, India was published recently as a preprint in medRxiv.
The researchers said that one of the reasons for the spread was the fact that rural areas experienced fewer restrictions on mobility. Also, the migration of daily labourers to rural parts was another factor.
Estimated RT-PCR positive proportions suggested that the epidemic was growing rapidly during August. The proportion of those testing positive on RT-PCR ranged from 1.5 to 7.7 per cent in rural areas and 4.0 to 10.5 per cent in urban areas suggesting a rapidly growing epidemic.
The study sample was drawn from an existing, representative sample of a panel survey—the Center for Monitoring Indian Economy’s Consumer Pyramids Household Survey (CPHS). The Karnataka seroprevalence study draws a random sample from CPHS’s 9,717 households in Karnataka separately for the urban and rural strata.
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