29% of Delhiites have Covid antibodies: Serosurvey

Close to one-third of Delhiites were exposed to coronavirus as Covid-19-specific antibodies were found in their blood, results of Delhi’s second serological survey revealed on Thursday.

Carried out on more than 15,000 people, the survey confirmed the presence of such antibodies in the blood of 29% of people, even though there may not be any sign of disease in most of them.

This is a 6% jump from the previous serosurvey in Delhi, which may be an indication of a silent spread of the virus without causing the disease.

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Carried out in each of the 11 districts, the survey looked for Covid-19 antibodies in the blood of an individual. The presence of such antibodies is possible when the person has been infected by the virus, but as the two serosurveys have shown, Covid-19 infection does not necessarily translate into the disease.

Public health specialists admit that it is a positive sign, but cautioned against early celebration.

“It is nearly half-way mark of reaching an empirical goal (60%) of reaching population immunity, after which the susceptibles can no longer sustain the disease transmission. It might be best to treat this as good progress. The external manifestations of reaching population immunity are when we get to see test positivity of around 5%, and cases progressively decrease,” Giridhar R Babu, professor of epidemiology at the Public Health Foundation of India told DH.

Results of the first serosurvey in Delhi, as well as those conducted in Mumbai and Pune, showed similar trends.

The first Delhi survey demonstrated the presence of the Covid-19 antibody in 23.48% of 21,000 people who participated in the survey. In comparison, the second survey threw up a figure of 29% (males: 28.3%; females: 32.2%).

Since Delhi has a population of 1.9 crores, this means lakhs and lakhs of people were infected. The existing detection system, however, could capture 1.56 lakh positive cases in Delhi.