The Rajiv Gandhi Government General Hospital (RGGGH) has taken up a pilot study among COVID-19 positive patients, in whom S-gene dropout was identified, by repeating the RT-PCR test every alternate day to check how early they turned negative for the infection.

Last week, a cluster of COVID-19 cases surfaced at RGGGH after a patient with diabetes turned out to be positive for the infection. Following this, 3,965 persons were tested from December 17 to 27 of which 94 were found to be COVID-19 positive. Of this, S-gene dropout, a marker for the Omicron variant of SARS-CoV-2, was identified in the samples of 64 persons till Tuesday. All of them were asymptomatic, according to hospital authorities.

E. Theranirajan, dean of RGGGH, said till Monday 51 patients (28 healthcare workers and 23 patients) had S-gene dropout, while it was identified in 13 more persons on Tuesday. Six of them were cases of re-infection. “We launched the pilot study a few days ago. We have been lifting swabs from the 51 patients with S-gene dropout every alternate day to know how early they became negative for the infection. The pathophysiology of the new variant is different from Delta variant. This seems to stay in the bronchus and trachea. All 51 patients are having oxygen saturation level of 99% that shows that the infection does not involve the lungs, he said.

He pointed out that unlike in Delta variant of SARS-CoV-2 in which the median incubation period was five days, Omicron variant’s median incubation was 2.5 days. “We have readied a proforma for patients in whom S-gene drop was identified and results of whole genome sequencing are being awaited. It is a challenge to keep all patients for 10 to 14 days in hospital. So, we are looking at their recovery period. If we study and understand this, we can plan for further isolation and discharge. Earlier, patients were positive for COVID-19 for even 30 days and we want to see if the new variant is of a short duration,” he said.

This documentary evidence would help doctors in decision-making.