Experts at Pune's B J Medical College, the Indian Institute of Science Education and Research (IISER), and the National Institute of Virology have said their assessment of the latest coronavirus sub-variant XBB.1.16 shows it has not caused severe infections. The assessment comes at a time when the World Health Organization (WHO) has declared that Covid-19 is no longer a global emergency. It was posted recently on medRxiv, a preprint server for health sciences. However, when asked about the latest assessment, Dr Subhash Salunkhe, Chairperson, Maharashtra's Covid-19 task force, warned against complacency. “Its increased transmissibility and immune evasive properties are alarming and hence we cannot afford to be complacent,” said Salunkhe. Dr Rajesh Karyakarte, lead author of the study and Professor of Microbiology at B J Medical College, said the identification of a new SARS-CoV2 lineage (XBB.1.16 variant in this case) should be followed with a prompt assessment of clinical features and outcomes. “There should be an immediate sharing of genomic data to public databases. Both these measures, clinical genomic surveillance, and detection and naming of new lineages can provide prompt evidence to aid policymakers in making informed public health decisions and interventions,” Dr Karyakarte, who is also a member of Maharashtra's Covid-19 task force, said. As part of the study, researchers downloaded 2944 sequences from the Global Initiative on Sharing All Influenza Data (GISAID) database (from December 1, 2022, to April 8, 2023). Of these, 2856 were included in the study and the sequences from India were dominated by the XBB.1.16 lineage (36.17 per cent) followed by XBB.2.3 (12.11 per cent) and XBB.1.5 (10.36 per cent). A total of 693 sequences were from Maharashtra and of these 386 were included in the clinical study. Of the 386 cases, 276 (71.50 per cent) were XBB.1.16. Their findings showed that 92 per cent of those with XBB.1.16 infection in the sample size of 276 had symptomatic disease – with fever (67 per cent), cough (42 per cent), rhinorrhoea (33.7 per cent), body ache (14.5 per cent), and fatigue (14.1 per cent) being the most common symptoms. Among these cases, 91.7 per cent were vaccinated with at least one dose of the vaccine against Covid 19. Around 25.7 per cent needed hospitalisation and seven (2.5 per cent) succumbed to the disease. The majority who died were above 60 years and had comorbid conditions. Dr Karyakarte also pointed out that the study concerns only those cases where samples were sequenced that in turn was a subset of those who were RT-PCR tested (most were symptomatic). Since its identification on March 4 this year, the XBB.1.16 lineage has already spread to 31 countries, with India reporting the highest percentage of sequences (32.47 per cent), followed by Brunei (4.50 per cent), and Singapore (3.21 per cent). XBB.1.16 is an XBB.1 sub-lineage characterised by unique mutations in the genome's spike. “The SARS-CoV-2 has undergone rapid evolution since November 2019, resulting in the emergence of competing lineages. Co-infections with different SARS-CoV-2 lineages can give rise to recombinant lineages,” Dr Karyakarte said adding their study showed that XBB.1.16 lineage had become the most predominant one in India. “However, this sub-variant has not caused severe infections. Due to the increased growth efficiency XBB.1.16 is progressively replacing all other co-circulating lineages in the country,” he added. Rapid monitoring of the lineage's growth rate by scientists and identifying the mutations helped understand that the sudden surge in a number of cases was due to a new, fitter, and immune evasive subvariant. According to Dr Krishanpal Karmodiya, Assistant Professor, IISER and one of the authors of the study, “The pandemic will eventually go down this way. This was a silent wave with not many hospitalisations. The way forward is to continue with sequencing and integrating data with hospitalisations”. Meanwhile, Dr Ishwar Gilada, Consultant, Infectious Diseases and Secretary General Organised Medicine Academic Guild-OMAG, welcomed the WHO decision. "The pandemic ended.. it may have ripples and can be endemic here and there. I am glad that finally, wiser counsel prevailed. We have been advising WHO as well as our Government for long," he said.
