The number of cases of COVID-19 without any clear epidemiological links – the source of infection is unknown – has been on the rise from different parts of the State in the past few days.
Public health experts and doctors have now raised questions as to why, despite claims of transparency, the Health Department has not been sharing the data of the two community-level sampling studies it did, to check whether there is unknown transmission of COVID-19 in the State.
Surveillance samples
Since April 23, 900 sentinel surveillance samples are being collected by the Health Department every week from across the State from health workers, pregnant women, and police personnel, who are at higher risk of contracting the disease, and sent for RT-PCR testing for COVID-19. On April 26, the State did a one-day mass ‘augmented’ sample surveillance amongst similar groups in the community, when 3,000 plus samples were collected for testing.
However, while the Health Department has given specific directions that the surveillance study samples are not to be mixed up with routine samples (which are from a quarantined pool of people with history of travel to COVID-19-affected places), the test results have not been kept separate.
The number of new positive cases — mostly active, asymptomatic cases — from the surveillance samples are important as these are cases wherein the source of infection is unknown and indicate pockets of silent disease transmission here.
‘Indeterminate’
But instead of announcing the details of these surveillance studies separately, all positive cases from both studies are announced with routine sample results as cases that contracted the infection through “contacts.”
These cases should be considered separately and spatio-temporal analysis of the aggregate data will indicate the geographic area from where these positive cases are consistently reported. The daily bulletin mentions the number of surveillance samples from sentinel survey which became negative, but not the number of positives.
The bulletin on Friday said of the 3,128 samples tested as part of augmented survey, four were positive and that 35 samples were being re-tested or still remain “indeterminate”.
The total samples tested as on Friday was 27,150, which suddenly became 31,183 on Saturday. Does that mean the 3,128 samples of augmented survey were added to the total figure? But the numbers just do not add up.
Questions are being raised now on why the actual data on the community surveillance studies has not been placed in the public domain. How many samples in each population groups were tested and what was the positivity rate in each group? Which is the population sub-group at high risk? In a disease where asymptomatic cases is a major driver of transmission and with PCR tests picking up only 70% of the cases, one would expect more than four positives from 3,128 samples.
‘Contacts’ go up
“Given the huge number of unknowns regarding COVID-19 and the fact that asymptomatic transmission is something which no government can control, it is foolish to assume that the virus will behave differently in Kerala. Even going by the official figures, the number of ‘contacts’ seems to be climbing, indicating that community transmission may have already begun,” a senior public health professional in Health Service said.
