Chennai, Aug 24 : The Tamil Nadu Health Department is gearing up to conduct serum surveillance survey in ten districts of the state following the decline in the number of Covid-19 positive cases. The health department will announce the date after the approval from the state government. The previous serum surveillance study was conducted in June in Virudhanagar, Chennai, Madurai, Tenkasi, Theni, Erode, Coimbatore, Nagapattinam, Namakkal, and Karur. While the first five had the highest serum positivity rate, the last five had the lowest. The department will be conducting the serum surveillance test in the top five and the bottom five districts and is for reconfirming the testing details of the previous survey. According to information from the health department sources, around 660 blood samples would be collected randomly from a district the check the presence of antibodies. In Coimbatore, according to a senior official of the health department, samples would be collected from only 22 clusters instead of the 42 clusters from where samples were collected during the previous survey. Officials also said that anyone above the age of 18 could be approached to collect samples for a random survey from the selected clusters. With cases are on the decline and the state opening up almost all of facilities to the public, the health department wants a scientific analysis on the ground situation and to take necessary precautions based on the trend. /IANS