Dr Manoj Murhekar, director of the ICMR-National Institute of Epidemiology, told TOI that community monitoring would be conducted in the top 10 cities with the highest incidence of Covid-19 in the next phase of the study. “The next phase will include Delhi and Mumbai,” he said.
As part of the community survey, health workers collect blood samples from 400 randomly selected individuals – one per person. Household – from 10 clusters in each district. These samples are then tested for the presence of IgG antibodies using ELISA tests developed by the ICMR-National Institute of Virology (NIV), Pune.
Dr. S K Sarin, the chairman of Delhi’s Covid-19 Task Force, said random testing would help know the community’s spread of the pandemic. “It will also tell us the extent of herd immunity in an affected population,” Dr. Sarin. Delhi needs mass-scale antibody testing to reorganize the zones, he pointed out.
Currently, the city relies on real-time polymerase chain reaction (RT-PCR) testing for the Covid-19 diagnosis. It is considered the gold standard for testing the novel coronavirus but is not suitable for community monitoring. The test takes time and has high biosecurity and biosecurity requirements. It also involves taking samples from nostrils that many people tend to avoid, an official said.
Quick test kits, for example ELISA tests developed by ICMR-NIV, Pune, are faster to implement and their biosecurity requirements are less stringent. Apart from the ICMR-NIV, many such kits developed by other companies, some of them Indian, were approved last month.
The Delhi government had in fact procured 42,000 quick test kits for community monitoring of Covid-19 in the state. However, the ICMR instructed states not to use these sets – mainly imported from China – because their results were not reliable.
In New York, which has been severely affected by the pandemic, a random test showed nearly one in five people had been infected. It is a sign that herd immunity is developing in a significant population. “If we have similar results for, for example, a red zone, mitigation is possible. Focus can be shifted to the other zones, orange and green, to strategy to prevent the spread of disease, ”said an epidemiologist.