West Bengal on Wednesday launched a sentinel surveillance in all its 23 districts to find the current trend of COVID-19 pandemic in the state, a senior official said.

At least 12,000 samples will be collected during the survey which will continue till April 29, he said.

Going by the sudden rise in the number of coronavirus cases in other parts of the country, we have decided to carry out sentinel surveillance to find out the trend here. We are cautious, the official told PTI when contacted.

The samples collected will be sent for COVID-19 tests at the College of Medicine and JNM Hospital at Kalyani to find out the trend of the contagion, he said.

Along with the survey, the state government will continue with its search to find out whether any new variant of coronavirus has evolved in the state, he added.

Sentinel surveillance is monitoring of the rate of occurrence of a specific disease through the voluntary network of doctors and laboratories aiming to assess the stability in health levels of the population of a particular region.

Bengal's COVID-19 positivity rate is 0.39 per cent and the number of active cases is 2o,18,067, according to the health department bulletin of Tuesday.