KOLKATA: The Kolkata Municipal Corporation on Tuesday started IgG antibody tests among people in some of the worst-hit areas to check for community spread of the coronavirus, a senior official said.
Samples were taken from residents of ward numbers 11, 28, 61, 82 and 90, all of which have a large number of containment zones, he said.
Samples of 100 people in each of these wards were collected and they will be sent to the ICMR's laboratory in Chennai for testing.
"We had got guidelines from the ICMR (Indian Council of Medical Research) and according to that we have started conducting these tests from today," chairman of the KMC board of administrators Firhad Hakim said.
The apex health research body, ICMR, has advised states to conduct sero-survey to assess the proportion of population, including asymptomatic individuals, exposed to coronavirus infection.
Sero-survey involves testing of blood serum of a group of individuals for the presence of antibodies against that infection to know who has been infected in the past and has now recovered.
In its advice to the states, the ICMR said periodic sero-surveys are useful to guide policymakers and stressed that IgG ELISA test should be used for carrying out such surveys.
Antibodies generally start appearing after two weeks of the onset of infection, once the individual has recovered, and last for several months.
"Therefore, the IgG test is not useful for detecting acute infection but indicates episode of SARS-CoV-2 infection in the past," the ICMR had said in a statement.
Kolkata recorded its highest single-day spike with 170 new COVID-19 cases on Tuesday, according to the state health department.
The state capital, which has reported the maximum number of cases in the state, saw its tally jumping to 3,946 with detection of the fresh cases, it said.
There are 2,097 active cases in the city at present, while 1,548 people have been discharged from hospitals so far.
In all, the state reported 415 fresh COVID-19 cases and 10 new deaths, it said.
The death toll in the state rose to 495 with the latest fatalities.
All the 10 fresh deaths were because of "comorbidities, where COVID-19 was incidental", according to a bulletin issued by the health department.
The total number of cases in the state soared to 11,909, of which 5,386 people are currently undergoing treatment in different hospitals, it said.
At least 534 people were discharged from different hospitals in the last 24 hours after being cured.
Four of the new deaths were reported from Kolkata where the death toll stood at 301, three from North 24 Parganas, two from Howrah, and one from South 24 Parganas districts, the bulletin said.
North 24 Parganas recorded 70 cases, 40 new cases were detected in Howrah, 31 in South 24 Paraganas, 18 in Coochbehar, 15 each in Hooghly and Purba Medinipore districts, 13 in Birbhum, 10 in Malda and nine in Paschim Medinipore district, it added.
Eight new cases were found in Nadia, five in Jalpaiguri, two each in Murshidabad, Bankura and Dakshin Dinajpur districts, the bulletin stated.
One case each were reported from Darjeeling, Kalimpong, Uttar Dinajpur, Purulia, Purba Burdwan, it added.
In the last 24 hours, 8,512 samples have been tested for COVID-19, raising the total number of tests to 3,51,754.
A constable of the Kolkata Police was among those testing positive for the disease and was admitted to a private hospital for treatment, sources said.
Over 200 personnel of the force have so far been infected by the deadly virus.