A large number of infected people in the capital remain asymptomatic, the govt’s sero-survey indicates
Survey was carried out by the National Centre for Disease Control together with the Delhi govt
Nearly six months into the covid-19 outbreak, 23.48% of Delhi’s population was infected with SARS-CoV2, revealed the findings of a sero-surveillance study released on Tuesday by the Union health ministry. The study also indicated that a large number of infected people in Delhi remain asymptomatic.
The study, commissioned by the health ministry, was carried out by the National Centre for Disease Control (NCDC) in collaboration with the Delhi government. “Eight out of the 11 districts have sero-prevalence of more than 20%. The central, north-east, north, and Shahdara districts in Delhi have sero-prevalence of coronavirus of around 27% as Delhi has several pockets of dense population," said Dr Sujeet Kumar Singh, director, NCDC.
The increase in testing and containment strategy undertaken in consultation with domain knowledge experts has resulted in bringing the rate of new cases from a covid-19 positivity rate of 37% in Delhi in the first week of June to the present level, the ministry said.
“However, 77% of the population is still vulnerable, which is a significant proportion. Therefore, the containment measures need to continue with the same rigour. The sero-surveillance was done in Delhi to estimate the prevalence of covid-19 infection among the general community of Delhi," said Singh.
“Non-pharmacological interventions, such as physical distancing, use of face masks or cover, hand hygiene, cough etiquette, and avoidance of crowded places, must be followed strictly," Singh said.
Survey teams were formed for all the 11 districts of Delhi for the study that was conducted between 27 June and 10 July. Blood samples were collected from selected individuals after taking written informed consent, their sera were tested for immunoglobulin G (IgG) antibodies and infection using the Covid Kavach Elisa approved by the Indian Council of Medical Research. It is one of the largest sero-prevalence studies conducted in India using Elisa testing, the ministry said.
NCDC collected 21,387 samples in line with lab standards for testing. “These tests are not diagnostic tests, but only provide information about past infection because of SARS CoV-2 in individuals who test positive. Antibody testing repeatedly done over time, which is sero-surveillance, generates important evidence for assessing the spread of the pandemic from time to time," the health ministry said.
“IgM (immunoglobulin M) antibody indicates the presence of active covid-19 infection, but does not give a clear picture of total exposure. On the other hand, IgG antibody remains in the body for a sustained and longer period. While antibody detection tests help assess the prevalence of infection in the community, RT-PCR tests and rapid antigen tests are actually helpful in treatment of individual covid-19 patients," said Singh.
Delhi has so far recorded more than 125,000 cases with over 15,200 active patients and 3,690 fatalities. The total tally in India reached 1,171,446 on Tuesday.
The government on Tuesday said that India is conducting 180 tests per day per million people, which is more than the adequate testing rate of 140 tests per day per million for a prolonged period, as specified in the WHO’s guidance note. Besides, the case fatality rate has dropped to 2.43%. Many states and UTs have a case fatality rate lower than the national average.