New Delhi: The second phase of the serological survey in Andhra Pradesh begins across nine districts in the state Wednesday.
The survey will be conducted over a period of seven days and is expected to collect 45,000 samples to analyse the infection levels of Covid-19.
In the first phase of the survey, conducted between 7 August and 12 August, samples were collected from four key districts of the state — Anantapur, Krishna, East Godavari and Nellore.
Krishna district had the highest exposure to the infection with 21.7 per cent seroprevalence, followed by Anantapur (16.7 per cent), East Godavari (14.4 per cent) and Nellore (8.2 per cent).
Dr K. Rambabu, general physician and professor of medicine who is the state Covid-19 coordinator, told ThePrint that once the second leg of the survey is complete, a cumulative result of the two sero surveys will be shared to derive conclusions about the level of Covid antibodies developed by the people of the state.
Serological surveys are an exercise aimed at detecting the true exposure of a population to a disease. They involve testing blood samples for antibodies and thus help detect even those people who may have recovered from the disease on their own without requiring medical assistance. In the case of Covid-19, this would include asymptomatic people who contracted and recovered from the disease without their knowledge.
‘A larger sample size this time around’
The key difference in the two surveys, explained Dr Rambabu, is the sample size.
“We took 3,750 blood samples from each of the four districts between 7 August and 12 August, but this time, we will gather 5,000 samples from each of the nine districts starting 26 August,” he said.
Explaining the process, he said, 1,000 samples in each district will be taken from those considered high risk, while the remaining 4,000 will come from the general population.
Senior citizens, health workers, police personnel, sanitation workers and migrants, among others, are considered to be in the high-risk category.
Around 60 per cent of the samples will be collected from containment zones. The blood serum samples will be tested for IgG antibodies using the Chemiluminescence Enzyme Immunoassays or CLIA method. IgG is a type of antibody that is produced in the blood after an infection.
District-wise epidemiologists will advise the government on the various aspects of the survey.
Participating in the survey is voluntary, and only those people who have not got tested even once for Covid-19 before will be allowed to give their blood samples.
As of Tuesday, Andhra Pradesh reported 3,68,744, Covid-19 positive cases.