Second phase of sero-survey to track exposure of Madurai’s population to Covid

MADURAI: The second phase of the state health department’s serosurveillance to measure the exposure of the Madurai’s population to the SARS-CoV-2 is underway here. A gold standard for measuring recent or past exposure to infectious diseases, serosurveillance is blood-serum-test programme done to detect and measure antibody levels produced against an infection.

The second phase of the sero-survey, which is being carried out in all districts of the State, began in Madurai on April 8 and will end on April 22, according to sources in the district health department. During the second phase, 1,240 samples would be drawn from the district’s residents in 38 clusters. Of the 38 clusters, 22 are in rural areas and 16 in the city limits, sources added.

How this is different from the one in first phase?
During the first phase in November last, only blood samples were drawn from the participants in all the clusters. This time, however, the surveyors would collect swabs as well in 5 of the 38 clusters, said Deputy Director of Health Services Dr KV Arjun Kumar. These five clusters have been identified by the Directorate of Public Health and Preventive Medicine, he added. Sample collection is complete in 10 clusters as on Wednesday, according to sources.

Know here: How will the tests be conducted?
Samayanallur Upgraded Primary Health Centre will test the total 1,115 blood samples collected from the district using the chemiluminescence immunoassay (CLIA) technique. The 125 swabs collected from the five clusters would be sent to the State Public Health Lab in Chennai for testing. 

‘Swabs for analysing positive indices,’ says senior official 
Asked whether the swabs are being collected to study the mutant strains of Coronavirus, a highly-placed official in the Directorate of Public Health and Preventive Medicine said they were being collected for analysing positivity indices. “A separate exercise will be carried out to collect swabs for studying the prevalence of mutant strains of Coronavirus in the State,” he added. 

The results of the first phase conducted on 26,135 samples by the Tamil Nadu Department of Health and Family Welfare across 37 districts in October-November last indicated that nearly one third of the State’s population (31.6%) was exposed to SARS-CoV-2. Madurai, from where 1,140 samples from 38 clusters were tested, had recorded 38% seroprevalence.

Commenced on April 8 
The second phase of the sero-survey, which is being carried out in all districts of the State, began in Madurai on April 8 and will end on April 22, according to sources in the district health department