INSACOG plans sewage testing for early prediction future waves
Coronavirus cases have risen nearly 23 times over the last month in West Bengal, pointing to a fourth wave in the state. However, senior public health experts said the disease seems to be endemic and less virulent this time.
On July 14, the state registered 3,029 cases. It has the second-highest daily number of patients in the country at present, with a positivity rate of around 19 per cent.
Kolkata and adjoining districts recorded the maximum number of cases. However, the current wave has spread to all parts of West Bengal already, as indicated by a recent sentinel survey by the state health department.
No new variant is suspected to be behind the surge, said an Indian SARS-CoV-2 Genomics Consortium (INSACOG) expert. However, the forum is exploring options to study sewage samples for early prediction of future waves.
The central government had set up the umbrella forum under the Union Ministry of Health and Family Welfare to carry out the genomic sequencing of the virus in India.
A frontline physician from Kolkata confirmed that the fourth wave had begun. “The actual number of affected people must be 10 times higher as most people are not getting tested,” said Ajoy Sarkar.
However, the lungs and other organs of patients do not seem as affected in the current cases, he said. “Only co-morbid patients are at risk. It seems that COVID is fast turning endemic like influenza,” he added.
Arup Haldar, another COVID specialist and pulmonologist, agreed. “Even in the case of co-morbid patients turning critical, we do not know the role of the virus behind the deterioration in health,” he said.
“The current wave, however, underlines that COVID is here to stay and will become endemic. It will continue to cause surges from time to time while not being very virulent,” Haldar said.
A senior state health department official also concurred that the virus did not seem as severe this time.
“We have around 700 hospitalisations in the state right now, even though there have been around 19,000 cases in last one week,” the official said, adding that the number of deaths is also fewer than in earlier waves.
Despite the surge in positivity, many hospitals have kept only one dedicated section and intensive care unit for COVID patients. During the previous waves, many health care units had turned COVID-only hospitals.
During the first wave in Bengal in October 2020, the number of deaths per day was around 60 at its peak. The figure more than doubled during the second peak in May 2021 and slashed to less than 30 at the height of the third wave in January 2022.
Right now, five deaths in a day have been the highest toll.
A sentinel survey in the second week of July shows that the positivity rate of at least nine districts and two health districts in the state — including Kolkata — is above 10 per cent.
The survey carried out randomly among the non-COVID hospital patients found that the test positivity rate was 24.6 per cent in Nandigram health district and 23.8 per cent in North 24 Parganas.
The figure was above 10 per cent in Darjeeling, Uttar Dinajpur and the health districts of Basirhat, Howrah, Purba Bardhaman, Kolkata and Nadia.
A health advisor of Kolkata Municipal Corporation (KMC), Tapan Mukherjee, also told Down To Earth that the number of cases was increasing in the city.
“We had 342 RT-PCR positive cases on July 4, while on July 14, the figure jumped to 630 cases,” Mukherjee said.
Another KMC expert claimed that the virus had spread to a significant part of south Kolkata.
While there are claims that a new variant, BA 2.75, may be triggering the recent wave in India, including the cases in West Bengal, experts of INSACOG disagree.
“So far, we have not found any new variant triggering the current surge. The BA 2.75 is just a reclassification and is not much different from BA.2 despite some mutations in reality,” said Saumitra Das, a senior advisor to INSACOG.
However, another variant, BA 2.38, is increasing gradually and may become more dominant with time, Das said.
“It seems a lack of COVID -appropriate behaviour and throwing caution to the wind are responsible for the spike. Many thought that the pandemic was gone for good, but the latest surge shows that it is turning endemic,” added the scientist.
INSACOG has started exploring the possibility of setting up an early warning system, maybe one or two weeks before a surge, by monitoring sewage samples, Das said.
Sewage samples are monitored for viral diseases like Polio to ensure better public health management in case of future spikes.
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