Delhi's sero-prevalence study finds 23.48 per cent people affected by COVID-19

Delhi's seroprevalence study has found that 23.48% of the people have been affected by COVID-19 in the city, which has several pockets of dense population, the Union Health Ministry said on Tuesday. The study, which was conducted from June 27 to July 10 by the National Center for Disease Control (NCDC) in collaboration with the Delhi government, also indicated that a large number of infected persons remain asymptomatic, it said.

A serosurvey involves testing of blood serum of individuals to check for the prevalence of antibodies against infection.

"The results of the seroprevalence study show that on an average, across Delhi, the prevalence of IgG antibodies is 23.48%. The study also indicates that a large number of infected persons remain asymptomatic," the ministry said in a statement.

"This implies that nearly six months into the epidemic, only 23.48% of the people are affected in Delhi, which has several pockets of dense population," said the ministry, attributing it to efforts taken by the government to prevent the spread of infection including lockdown, containment and surveillance measures, including contact tracing and tracking, as well as citizen’s compliance to COVID appropriate behaviours.

It, however, said that a significant proportion of the population is still vulnerable and therefore, the containment measures need to continue with the same rigour. Non-pharmacological interventions such as physical distancing, use of face mask/cover, hand hygiene, cough etiquette and avoidance of crowded places etc., must be followed strictly, it underlined.

For all the 11 districts of Delhi, survey teams were formed. Blood samples were collected from selected individuals after taking written informed consent and then their sera were tested for IgG antibodies and infection using COVID KAVACH ELISA approved by the Indian Council for Medical Research.

It is one of the largest seroprevalence studies conducted in the country using the ELISA testing. A total of 21,387 samples were collected as per lab standards and were tested.

The tests help in the identification of the presence of antibodies in the general population. The test performed is not a diagnostic test but only provides information about past infection due to SARS-CoV-2 in individuals who test positive, the ministry said. According to the Health ministry's data updated at 8 am, Delhi's COVID-19 caseload increased to 1,23,747 while the death toll rose to 3,663 on Tuesday.