New worry: Spike in test positivity rate in Tamil Nadu

UDHAGAMANDALAM: With cases going up every day, the positivity rate of Covid-19 infection – the percentage of people testing positive among the total number people being tested — for the viral infection changes is increasing, although not steadily on the graph. Nevertheless, the meticulous contact tracing and high number of testing by the district is now being lauded by public health experts.
On April 22, the positivity rate of the virus stood at 4.5%. It went down to 3.3 on April 28, but rose up to 6.1 on May 1. But the weekly average of test positivity rate steadily moved 3% to around 6% over the last three weeks. “Weekly average indicates a steady increase in infection rate. Daily rates can vary due to several factors,” said a senior public health official.
The positivity rate touched 9% on Tuesday, when the district reported 117 new cases – the highest single day rise since the beginning of the pandemic. With 427 active cases, the number of containment zones in the district has also doubled to 12 from 6 in one week. The district, which has four testing labs (in private) has done 5.71 lakh tests per million people – the highest in the state, followed by Chengalpet (5.60 lakh per million) and Kancheepuram (5.53lakh per million).
Tamil Nadu has tested 2.62 lakh per million compared to the all India average of 2.89 lakh per million.
With high testing, the district has been able to detect cases early. The state statistics show the incidence of Covid per million people in the district is 14405 compared to 14446 in the state, but the case fatality rate – percentage of deaths over the total number of people tested positive – is the lowest in the state at 0.5%. “We test more so we can isolate positive cases early. We track down all contacts of positive cases and test them,” said Dr P Balusamy, deputy director, public health.
On an average, the district tests at least 21 highrisk contacts of every positive patient and all contacts undergo RTPCR tests. “The Ooty Government Medical College Hospital (GMCH) has a capacity of testing 1219 swabs in a day. We are expecting another testing machine by this week. When that comes, we can do up to 2000 tests,” he said.
The district has now been shown as a model for almost all high incidence districts. “When we test aggressively the number of cases increase, but we will see a plateau sooner than districts that don’t spread,” said state health secretary J Radhakrishnan.