Low positivity rate in 2nd test, but q-centre infections not ruled out

Nagpur: Allaying concerns of many citizens, the public health department data regarding number of suspects found positive in first and second tests shows that most were already carrying the Covid-19 virus when they were placed in institutional quarantine centres in the city.
The district administration and health authorities had faced severe flak from suspects, who alleged they were “deliberately kept and forced to use common facilities to inflate numbers of positive cases”. Though nodal officers at these centres had tried to convince suspects that the incubation period ranges between 2 to 14 days, the explanation hasn’t changed the mind of the latter.
As on July 11, around 11,810 high risk suspects were quarantined at different places in the city and outside since March 5. Of these, total 1,248 persons were found positive. Among those testing positive, 1,021 tested positive in the first test done soon after admission. There were 227 suspects who tested negative at first but turned positive in the second sampling, which is done before completion of 14-day isolation period.
Nagpur district had reported 2,234 positive cases as on July 11. This means 55.88% cases came from quarantine centres. The total positive cases are just 10.56% of total admissions at quarantine centres. First-test cases amount for 8.64% while second-test cases are 1.9% of the total admissions.
Besides the 11,810 admissions, the district administration had quarantined another 320 suspects at the now shut Lonara College and Chinchbhuvan’s Prozone Palms. As data of first and second is not available, TOI excluded them in the analysis.
Health officials believe those testing positive in second sampling are the ones who failed to maintain Covid distancing during their stay at centres, though it can’t be proved epidemiologically if they contracted the infection before or after admission.
A top health official said either way it is difficult to say what makes a sample test negative first and positive later. “It is true the virus is not detectable in first sampling because of low viral load. By the time second one is done, a suspect has come in contact with other high risk persons, even as there is likelihood that the viral load increased enough to be detected,” the official said.
Dr Meena Mishra, professor and head of the department of microbiology at AIIMS, Nagpur, said suspects are kept at quarantine centres only when they fulfil certain conditions. “Swabs are tested using RT-PCR for detecting RNA material to confirm presence of virus. But there are many factors which govern the results. In this test, sometimes a person tests negative because of early phase of infection or because the viral load is less,” she said.
Dr Mishra attributed the second test positive cases to lack of awareness and casual approach. “After testing negative in first test, people feel nothing is going to happen to them and they forget to follow distancing guidelines,” she said.
Infogfx
Quarantine centre —— total admissions ———————— 1st test +ve —————2nd test +ve———— total
VNIT —————— 2033————— ———————— 211————————- 35——————— 246
MLA hostel ————— 2153 ———————————— 124————————- 20———————- 144
Vanamati ————— 591 ——————————— 44 ———————— 0—————————44
Ravi Bhavan ————435 ———————— ———19—————————9——————— —— 28
Symbiosis ——————— 1872 ———————— ———79 ————————— 41———————— 120
Pvt Hotels ———————— NA ———————— — -17—————————-1 ————————- 18
Pachpaoli Police Qts——— 2856———————— ——426 ————————-59———————— 485
RPTS —————— ——— 785———————————- 36 ———————— 5——————————-41
NU hostel ———————663———————— ————- 20———————- 30 —————————-50
Raj Nagar PWD Qts——— 186—————— —————— 38———————— 20—————————- 58
Morris college hostel—— 236—————— ————— 7 ———————— 7 —————————— 14
Total ———————- 11,810—————————- 1,021———————— 227—————————- 1,248