New Covid strain: 'Can’t rule out presence of virus variant in India'

MUMBAI: As there are no quick diagnostic tests to check for the new ‘UK Covid strain’, it is impossible to completely rule out the possibility of it already circulating in parts of the country. Experts have hence begun working on ways to test and sequence existing Covidpositive samples to look for the

new mutant strain

.


For example, BMC’s Molecular Diagnostics Laboratory at

Kasturba Hospital

has devised a unique way to sift through samples collected and stored at different points of time since September. Microbiologists there will look for samples that did not show the ‘S gene’ (on the coronavirus) during RT-PCR tests. “We’ll check for positive samples that have missed the Sgene detection and get them sequenced,” said Dr Jayanti Shastri, who heads the Kasturba diagnostics lab. “I’ve already asked my team to retrospectively check for such samples. We will further get them sequenced at NIV, Pune.”


For a swab sample to be certified as Covid-19 positive, the RT-PCR test needs to identify two

genes

located on the Covid-19-causing coronavirus Sars-CoV-2. The kits in use usually detect N, S and ORF genes, among others. “Detection of any two gene targets is termed Sars-CoV-2 positive,” said Dr Shastri. However, in the UK-mutated strain, the S gene target is not detected.




Hence, the lab’s decision to look for samples in which the Sgene did not show up. The new variant is responsible for 62% of the new Covid-19 cases in the UK since September. A few cases have been found in Australia, Italy, Iceland and Denmark.

UK government experts said that accuracy of testing had been affected to some extent by the arrival of the mutation. “There are reports of a South African mutation that is also worrisome in its ability to spread quickly,” said Dr

Shashank Joshi

, who is a member of the Maharashtra government’s task force on Covid.

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