The Andhra Pradesh government has decided to carry out a sero-surveillance in the state to check how many people may have been infected by the coronavirus. Krishna, Nellore, Anantapur and East Godavari are the four districts that have been shortlisted for the sero-surveillance. Sample collection began on Thursday. The training was also imparted to all the concerned officials from the various districts. Sero-surveillance will help officials understand the spread of the disease in the state.
According to the initial plan, 3600 samples would be collected from Vijayawada as part of a pilot project. The city, located in Krishna district was chosen for carrying out sero-surveillance. TNM had reported this story on July 26. Later, after multiple rounds of discussions and review meetings, the government has now decided to carry out the sero-surveillance on a much bigger scale.
As part of the sero-surveillance being carried out, a total of 15,000 samples are being collected from four districts in the state. Those participating in the survey will be informed about voluntary consent and only those who have not got tested even once before will be allowed to give their blood samples. The samples will then be tested for IgG, a type of antibody that is produced in the blood after an infection.
According to experts, the only way to prevent further spike in infections or find out how many people have been already infected is to check the presence of antibodies in people. Sero-surveillance is a globally used and trusted standard which measures the level of antibodies in people due to a certain infection.
Delhi and Mumbai had carried out sero-surveillance. While in Delhi it was found that at least 15-20% of the population had recently been exposed, in Mumbai it was found that 57% of the people in slums and 16% of people in residential areas had already been exposed and were immune to the SARS-CoV-2 virus.
Explaining details of sero-surveillance, Dr K Rambabu, General Physician and Professor of Medicine, who is also the state COVID-19 coordinator, said, “A total of 15,000 samples will be collected. Out of the total, 3750 samples will be collected from each of the four districts. Out of the 3750, 3000 samples will be collected from the general population and 750 will be collected from the high-risk zones.”
“Out of the 3000 samples to be collected from the general population, 2400 will be from containment zones and 600 will be from the non-containment zones. The containment zones will further have a division, 70% will be from the rural areas and 30% from the urban areas.”, added Dr Rambabu.
The sero-surveillance will be as per the guidelines laid down by the Indian Council for Medical Research (ICMR). There are several guidelines to be followed in terms of sample collection. If there is a village considered, then samples have to be collected from north-east, north-west, south-east and also south-west. If a house has four members of a family, only one person can be tested from the house. Only one house can be chosen from ten houses in a locality.
As per the ICMR guidelines, if there is a single female in the house, her sample is taken. If there are two females in the house, the older female’s sample is taken. If there are four men in a house and there is no female, then the older male’s sample is considered. Sample collection is a laborious process and has to be done very carefully to ensure the most accurate results. Experts say it is the most important part of the surveillance process.
Krishna, East Godavari, Anantapur and Nellore have been chosen to cover all the regions in the state. Explaining the reason for shortlisting these four districts, Dr K Rambabu said, “Krishna and Anantapur districts were chosen because we want to see if around 15-20% of the population already have antibodies. The numbers have been high in both these districts.
East Godavari has been seeing a surge. We want to check whether the district is still in the safe stage and whether there is any reason to worry. Hence East Godavari was chosen. In comparison, Nellore district has been reporting a lesser number of cases, hence we chose Nellore as one of the districts. We wanted to know whether there is already a large presence of antibodies or if there is still a chance for a spike.”
As of August 6, Anantapur has recorded a total of 20,061 COVID-19 cases, East Godavari 26,229, Nellore 9917, and Krishna 8679 cases.
“The process began today. We have set a target of one week. It may extend to around 10 days. Sample collection is what takes the most time. Once the samples are collected, on a daily basis it is sent to the labs for testing. Then epidemiologists, statisticians and other experts have to work on the test results and infer the conclusion,” said Rambabu.
Out of the four districts, only two districts have their own lab. Samples collected from Krishna and Nellore will be tested in the labs in the districts itself. Samples collected from Anantapur district will be sent to Krishna district and samples from East Godavari will be sent to the lab in Guntur for testing.
“In around four hours around 50 samples can be tested. If shifts are continuously working, in a day only around 350 samples can be tested in one lab. Testing is one of the main limitations in the process of sero-surveillance as it takes a long time,” explained Dr K Rambabu.
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