Wastewater surveillance shows increasing COVID-19 viral load in India
According to the latest data released by the Union Health Ministry on May 31, India registered 685 more active cases, taking the total number of COVID-19 cases to 3,395 since January this year. At 1,336, Kerala has reported the most number of COVID-19 cases, followed by 467 in Maharashtra. The small number of cases reported in India follows a similar rise in cases first seen in some Southeast Asian countries, including Singapore, Hong Kong, and Bangkok.
Based on data available from sentinel sites, the World Health Organisation (WHO) on May 28 said that global SARS-CoV-2 activity has been increasing since mid-February 2025, with the test positivity rate reaching 11%; the rise has primarily been in the Eastern Mediterranean, South-East Asia, and Western Pacific regions.
Wastewater surveillance data from Bengaluru suggests that COVID-19 viral load increased significantly in the last two weeks, with the increase in the last week being higher than the previous week, says Dr. Rakesh Mishra, Director of the Bengaluru-based Tata Institute for Genetics and Society (TIGS). The rise in viral load in wastewater was seen days before COVID-19 cases were reported. “There is a clear indicator of a silent wave with heavy viral load in wastewater,” he says. Samples from about a dozen sewage treatment plants are routinely tested by TIGS in Bengaluru. In Vijayawada, the viral load in wastewater is staying constant or reducing a bit. “But it is too early to say anything,” says Dr. Mishra.
According to data released by the Karnataka health department, the positivity rate based on testing also shows an increase in the last few days. On May 28, the positivity rate was 10%, which increased to 24% on May 30.
Wastewater surveillance in Pune showed the first signal on April 22. Since May 6, there has been an increase in viral load, and samples from all 10 sewage treatment plants show positivity, says Dr. Mahesh S. Dharne from the Pune-based National Chemical Laboratory. “There is a gradual increase in viral load in the sewage samples. This reflects an increase in COVID-19 cases in the community,” Dr. Dharne says.
COVID related deaths
Four COVID related deaths have been reported from Delhi, Karnataka, Kerala, and Uttar Pradesh on May 31, according to the Union Health Ministry. A total of 26 COVID related deaths have occurred till now, the data indicated.
UPDATE:
As of June 2, there are 3,921 active COVID-19 cases and 32 deaths in India.
Published in The Hindu on May 31, 2025
