NEW DELHI: Public health experts say the sero prevalence study in Delhi gives “incredibly useful data” that can be assessed and be useful in comparing virus exposure rates in different parts of India and over different time periods in the same population.
On Tuesday, the Centre released the results of the serological survey which showed around 23% of Delhi’s population could have been infected with COVID-19 till first week of July.
The findings which primarily depict the situation when cases were increasing rapidly in the Capital along with the recent decline in fresh cases here are also viewed as positive signs though experts are quick to caution against complacency.
“The fall in daily case count and, more importantly, a fall in daily death count are good signs indicating a decline in the epidemic. However, we still need to maintain the vigour of public health surveillance and containment measures as well as disciplined adherence to masks, physical distancing and hand hygiene at personal level. There are still a large number of susceptible persons whom the virus can infect if we are careless in our conduct,” says Dr Srinath Reddy, president of Public Health Foundation of India.
Experts say while results from the survey in Delhi cannot be extrapolated to other parts of the country, the assessment of the findings, if correct, can help interpret data from other cities when similar studies are conducted in other parts of the country.
“The serological survey conducted in Delhi provides incredibly useful real-time data. This data has to be assessed carefully and if the interpretations are correct, it can help in analysis of situation in other cities when similar studies are done there,” says Giridhara R Babu, who is part of the COVID-19 technical advisory group in Karnataka and an epidemiologist at the Indian Institute of Public Health.
So far, the projections were based on data and studies conducted in other countries like EU and China. The serological survey with over 20,000 samples in Delhi – conducted by the National Centre for Disease Control – is the largest such COVID-19 survey in the country, providing local data on infection trend.
This will also help the government in making policy interventions and upgrade health infrastructure and resources accordingly, experts say.
“This data can be helpful to answer questions like how many tests need to be conducted at a particular rate of infection or once the infection has declined to this level then how the transmission trends behaves, how much bed strength or resources required,” says Babu.
While experts say that the worst may be over in Delhi, they also warn against the false negatives from antigen tests and say that needs to be reconfirmed for correct assessment.
“While feeling relieved that many of the persons who tested positive were asymptomatic, we must recognise that antibody tests have false positive results too which boost the true prevalence rate,” says Dr Reddy.
While the survey points at a significant number of asymptomatic cases in Delhi, experts say that is consistent with the low death rates.
“This report should help to remove fear and stigma. It should also impress upon people that asymptomatic persons, who are many, can transmit the virus and therefore the critical importance of physical distancing,masks and hand hygiene,” Dr Reddy adds.