A detailed study conducted by professors at the University of Chicago and Duke University on the prevalence of COVID-19 in the state of Karnataka showed that the state has missed close to 30 million COVID-19 cases between the months of June and August 2020, the period at which COVID-19 was at its peak in the country.
Currently, Karnataka has reported close to 9.43 lakh COVID-19 cases.
Prof. Manoj Mohanan from Duke University and Prof. Anup Malani from University of Chicago conducted this study that was funded by ACT Grants and IDFC institute to assess the sero-prevalence in the rural as well as urban areas of Karnataka. With close to 1386 samples across the state, the study found that about 44.1% of the population in rural areas and 53.8% in urban areas in the southern state of Karnataka tested positive for antibodies to COVID-19 by the end of August 2020. They also found that there was no significant difference in the sero-prevalence between the rural areas and urban areas.
BOOM contacted both the professors to understand the key learnings of the study. Prof. Mohanan in an emailed response stated, "The result of early spread of the virus from urban centers (where much of the attention was in early days of the epidemic) to rural areas combined with testing policies that allowed testing only symptomatic cases. As several studies have reported, the vast majority of infections in India were asymptomatic. This rapid early spread is also consistent with the pattern of decreasing cases that India is currently witnessing."
The study did not only use antibody tests to determine the spread of the disease but also performed RT-PCR tests on a certain section of the participants. The RT-PCR showed that the proportion of those testing positive ranged from 1.5 to 7.7% in rural areas and 4.0 to 10.5% in urban areas. This is the only study so far that has used both the techniques to understand the spread of the disease.
The findings, based on data collected from a representative sample of households in 20 districts in the state, suggest that Karnataka alone had approximately 31.5 million cases of COVID-19 by then, relative to 3 million reported nationally in India at that time.
This study was conducted with the approval of the Karnataka government; however, they have not reacted to the findings of the study so far.
Due to the lockdown, Prof Mohanan also shared that data collection was challenging but their teams came up with innovative solutions to ensure that the collected samples reached the laboratories in time.
The same authors have also studied the spread of SARS-CoV-2 in Bihar, Mumbai, and Tamil Nadu.
The findings of this study published in the Journal of American Medical Association are very different from the nationwide second sero-survey conducted by the Indian Council of Medical Research during the same period. In that survey, only 7.1% of the population had developed antibodies against COVID-19.
During the same period, sero-surveys conducted in Delhi and Mumbai showed that in August over 29.1% of the population in Delhi and in June-July around 57% in Mumbai had developed antibodies suggesting that the cities were also not identifying several cases as only symptomatic people were being tested.
