Community transmission is said to happen when a person who has not been in contact with an infected person or travelled to a country where the virus is active tests positive. This implies the source of the infection can’t be traced, and containment becomes difficult.
The sample size per district will be 400 tests, and 75 districts have been shortlisted, where the study will be conducted to gauge the extent of undetected community spread, government officials told ET.
“It’s a cross-sectional study with a small sample size to ascertain the extent of exposure of Covid-19 in the population. The districts that are in the hotspots have been shortlisted,” said an ICMR scientist on the condition of anonymity.
Traditionally used in HIV testing, ICMR will use the enzyme-linked immunosorbent assay (ELISA) test for the survey. The ICMR had earlier decided to conduct the study using rapid antibody test kits.
“The criterion is to test those who are showing symptoms with no contact with Covid-positive patients,” added the government official. The ICMR has formed teams that will visit randomly selected households for the tests.
The ICMR and the health ministry have so far said that India has yet not seen community transmission. Earlier this week, union health minister Harsh Vardhan had reiterated this position.
No Community Transmission in Earlier ICMR Test
However, some public health experts and doctors are of the view that community transmission may be underway in some parts of the country that have witnessed a sharp spike in infections in the past few days. The ICMR study will shed light on this issue.
“…recently, its (the virus’) aggression has shown consistent progression. This, despite good lockdown procedures (with occasional outliers). Hence, it is likely that transmission within community and escape through densely positive hotspots has occurred. This phenomenon should be quickly researched and substantiated,” said Anoop Misra, chairman, Fortis C-DOC (Centre of Excellence for Diabetes, Metabolic Diseases and Endocrinology).
To rule out community transmission, the ICMR had in February and March carried out random sample testing of all patients with severe acute respiratory infections (SARI).
According to the ICMR, a total of 826 samples from people suffering from SARI/influenzalike illnesses were tested and none of the samples was found positive, which proved there was no community transmission at that time.
A pandemic or an infectious disease of this magnitude typically has four stages. In the first stage, only those who have travelled abroad to an affected area test positive. In the second stage, the virus spreads locally through contact with an infected person or with a person who has travelled to an affected country. At this point, every person who comes in contact with a positive case can be traced or isolated. India is currently said to be in this stage of local transmission.
Community transmission is the third stage. The fourth and final stage is when a large portion of a population gets infected. That is when it turns an epidemic.