Covid-19 Omicron variant: Tamil Nadu suspects second index case

CHENNAI: A 38-year-old woman hailing from Arni in Tiruvannamalai district, who returned to India from the Republic of Congo via Chennai on December 12, tested positive for Covid-19, health officials said on Thursday. An RT-PCR test done two days later showed an S-gene dropout – an indicator that she could be carrying the Omicron variant.
The samples have been sent for whole genome sequencing to labs in Bangalore and Pune. If samples return positive, she will be the second index case of the new variant in Tamil Nadu.
The patient has been admitted to Government Medical College Hospital in Tiruvannamalai, and her health condition is stable. Health workers are tracking the health condition of her close relatives although they have tested negative. She travelled to her home town from Chennai in a taxi.
The ICMR National Institute of Virology on Wednesday confirmed the first case of Omicron variant in Tamil Nadu. The patient is a 47-year-old man who travelled to Chennai from Nigeria via Doha on December 10.
The RT-PCR tests are conducted in whole for all the genes - N’, ‘S’, ‘E’ and ‘ORF'. The S gene is absent in Omicron. "Since S-gene is not detected during the test, it is called S-gene dropout or fall. The other gene targets are recognised. Although not a specific indicator, S-dropout is considered a proxy indicator for the new variant. In fact, organisations such as WHO are advising countries using this as an early warning.," said state DPH laboratory head Dr S Raju.
State public health staff and infectious diseases experts are now asking the state to expand the list of “at risk” countries or make testing mandatory for all international passengers. “The state has to create separate facilities for passengers so that there won’t be further community spread,” said a senior government doctor.