Random genetic sequencing recommended to determine if new strain is in circulation

December 30, 2020 02:20 am | Updated 02:20 am IST - Bengaluru

With the new variant of SARS-CoV-2 circulating in the United Kingdom since September 2020, there is a possibility that the new strain could have already been imported into Karnataka. To determine if the new strain is already present in the State, there is a need to conduct genome sequencing of random samples that tested positive in October-November, experts have said.

With the State not having witnessed a surge in cases in the last two months, experts said this could be because nearly 50% of the population is already exposed to COVID-19 here and hence there could have been cross immunity.

When the State’s first round of the seroprevalence survey was done in September, 27.3% of the population in the State had been exposed to the virus. This would have increased to over 50% now, according to experts.

Giridhar R. Babu, member of the State’s COVID-19 Technical Advisory Committee (TAC), said random samples should be subjected to genetic sequencing.

“A travel ban will only prevent the people from currently travelling and infecting here. We need to be sure that there are no major outbreaks missed anywhere in the State since September 2020 due to an import of infection. A sample of the cases should be subjected to genetic sequencing,” he said.

“Although it is unlikely that we may see a surge again, it is important to thwart the outbreaks in early stages. It seems mostly that the new strain is unable to find dense pockets of susceptible (uninfected) people. We need to be sure by testing random samples from all districts which have shown an active surge in cases,” he explained.

National strategy

V. Ravi, former head of the department of Neurovirology at NIMHANS, said as very few labs store samples of positive cases beyond two-three months, genome sequencing of U.K. returnees who had tested positive since September can be done.

“The national strategy now is to conduct genome sequencing of 5% random samples of international passengers who have tested positive since November 23. Epidemiological surveillance of the passengers, who have arrived in India since November 23 will also be conducted in the community through active follow up,” he said.

“The mutant strain more or less has the same features. While the precautions, symptoms, treatment protocol and virulence are the same, the new strain has a high transmissibility/infectivity. People will have to behave even more responsibly,” he said.

Cross immunity

C.N. Manjunath, nodal officer for labs and testing in the State’s COVID-19 task force, said nearly 50% of the population has already been exposed to SARS-CoV-2 actively or passively. “As a result, half the population in the State has developed immunity and this is bound to give protection against the new strain too,” he said.

“Various vaccine manufacturers and even the World Health Organisation (WHO) has said that the current vaccines being developed can effectively counter this mutation. If the vaccines can work against the new strain, then community immunity should also give protection,” he explained.

“As genome sequencing is expensive, it is not possible to test all samples. Instead, random samples of those who tested positive in the last two months should be subjected to this molecular test. This will help in knowing if the new strain is already here. If it is already there, we do not have to worry much,” Dr. Manjunath added.

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