One in every five person in Delhi is likely to have got infected with COVID-19, suggests the results of a sero-surveillance survey carried out by the Center for Disease Control (NCDC) in collaboration with Govt of National Capital Territory of Delhi. The study, commissioned by the Ministry of Health and Family Welfare, was on the basis of samples collected during 27 of June 2020 to 10 July, 2020.
The results of the sero-prevalence study show that on an average, across Delhi, the prevalence of IgG antibodies is 23.48 percent. The study also indicates that a large number of infected persons remain asymptomatic.
The rigorous multi-stage sampling study covered all the 11 districts of Delhi. Survey teams formed for the purpose collected blood samples of 21,387 individuals after taking written informed consent and then their sera were tested for IgG antibodies and infection using COVID KAVACH ELISA approved by Indian Council for Medical Research (ICMR). These test performed is not a diagnostic test but only provides information about past infection due to SARSCoV-2 in individuals who test positive.
Analysing the test results, the ministry of Health and Family Welfare has said that if after six months into the epidemic, only 23.48 per cent of the people are affected in Delhi, which has several pockets of dense population, it is the impact of the proactive efforts taken by the government to prevent the spread of infection including prompt lockdown, effective containment and surveillance measures, including contact tracing and tracking, as well as citizen's compliance to COVID appropriate behaviour.
At the same time, the ministry states that a significant proportion of the population is still vulnerable and 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 warned.
The study was one of the largest sero-prevalence studies conducted in the country using the ELISA testing to help in identification of presence of antibodies in the general population. Antibody testing repeatedly done over time i.e. sero-surveillance, generates important evidence for assessing the spread of the pandemic from time to time.