The results of sero-prevalence study conducted in the national capital show that over 23 per cent of Delhi’s population has been exposed to Covid-19. Experts opine that the spread of the virus has been significant. The study conducted in 11 districts also showed that a large number of infected people remain asymptomatic.
The study, conducted jointly by the National Center for Disease Control (NCDC) and the Delhi government, showed that on an average, across Delhi, the prevalence of IgG antibodies is 23.48 per cent. The sero test provides information about past infection due to SARSCoV-2 in individuals who test positive and it generates important evidence for assessing the spread of the pandemic from time to time.
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A sero-survey involves testing of blood serum of individuals to check for the prevalence of antibodies against an infection.
Elaborating on the results, Professor K Srinath Reddy, epidemiologist and president of the Public Health Foundation of India (PHFI), says that the spread of the virus has been significant in the capital.
Speaking to Outlook, Reddy said that the result shows that the virus has been transmitting freely and a large population of the capital is already exposed to it.
“I would say that 23.48 per cent is an extensive spread. That means quite a large percentage. Even New York reported between 20-30 per cent. Stockholm reported only 7 per cent then they corrected it to over 10 per cent. Most other cities reported only about that much,” he says.
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A total of 21,387 samples were tested for the study conducted from 27 June 2020 to 10 July 2020, according to a statement by the Union Health Ministry.
In its statement, the Health Ministry said that “nearly six months into the epidemic, only 23.48 per cent of the people are affected in Delhi, which has several pockets of dense population.”
However, Dr. M C Mishra, former director, All India Institute of Medical Sciences (AIIMS) says that the high percentage of exposed numbers is a clear indication of community transmission.
“This is what we have been saying all along. The government denies that there is no community spread. If one-fourth of the population of Delhi shows past exposure to the virus, it means community transmission,” says Dr Mishra.
“Anything above 15 per cent is significant. In the last survey, they had less than 5 per cent who had developed antibodies,” he says.
According to the ministry statement, blood samples were collected from selected individuals and were tested for IgG antibodies and infection using COVID KAVACH ELISA tests.
Dr Reddy says that Antibody testing must be repeated after a couple of months to assess whether there’s further change or not.
“We should also assess the results zone wise. The most affected ones and the less affected. That will also determine our strategy of containment. In some zones, which have been less affected, we may have to be much more careful about surveillance and ensure that they are not exposed that much,” says Dr Reddy.
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The ministry, in its statement, also warns that containment measures should be continued as a significant proportion of the population is still vulnerable.
“Non-pharmacological interventions such as physical distancing, use of face mask/cover, hand hygiene, cough etiquette, and avoidance of crowded places, must be followed strictly,” it added.
Dr Reddy echoes similar views. He feels that the government should adopt strict containment measures to check further spread.
“The important thing is that cases coming down are related to public health measures. But the fact that it has already affected a large chunk of the population demonstrates that there was a free passage of the virus earlier. By doing containment measures, we can still prevent transmission,” he adds.
