LAUSR

Until February 2023, the majority of COVID‐19 cases were associated with SARS‐CoV‐2 subvariants, such as BF.7, BQ.1, BQ.1.1, and XBB.1.5, and XBB.1.9. However, the recent surge in cases has been precipitated by a novel Omicron XBB.1.16 variant, dubbed “Arcturus.” First detected from samples collected in January 2023, XBB.1.16 has rapidly spread to over 31 countries by late March 2023, and is reported to have originated in India, where it is predominant and has replaced other strains of the virus. Cases have also been reported in several parts of Europe, and countries such as Australia, Britain, Brunei (4.50%), Canada, India (highest number of sequences globally at 32.47%), Indonesia, Singapore (3.21%), and the United States. In the United States, the cases caused by XBB.1.16 strain sore from 0.21% in late February, to 3.96% in March, and 7.2% in mid‐April 2023. Owing to such an increase in cases, on March 22, 2023, the World Health Organization (WHO) designated XBB.1.16 as a variant under monitoring status, and later as a variant of interest on April 17, 2023. Nextstrain/Nextclade has promoted XBB.1.16 as a novel clade, 23B. Currently, XBB.1.16 is one of the seven variants of SARS‐CoV‐2 currently being monitored. Compared with the parental XBB.1.5 variant that bore the spike protein mutation, F486P, XBB.1.16 variant presents two additional mutations, viz. E180V and T478R, as illustrated in Figure 1. Furthermore, XBB.1.16 has an effective reproductive number (Re) 1.27‐ and 1.17‐fold higher than the previous XBB.1 and XBB.1.5 variants, respectively, suggesting higher infectivity and transmissibility rates. Recent reports suggest that the XBB.1.16 variant demonstrated robust neutralization resistance against variants such as BA.5 (37‐times vs. B.1.1) and BA.2 (18‐ times vs. B.1.1). This suggests a conspicuous immune evasion property of XBB.1.16, compared with its parental variants. This immune‐evasiveness could be attributed to differences in its antigenicity compared to XBB.1.5 as well as nonspike protein mutations which expedite the viral growth rate. These factors have added to the virulence of its strain, and though not very significant, it is approximately 1.2 times more infectious than the XBB.1.5 variant. While these results suggest a greater infectivity and pathogenicity than its previous strains; its epidemiological impact remains to be studied further. With 50 000 active cases; cases mounting up to 11 000 per day, and 29 deaths in a single day, the Health Ministry of India, registered the highest jump in COVID‐19 cases, potentially linked to XBB.1.16. An analysis of the distribution of SARS‐CoV‐2 lineage sequences in India, retrieved higher percentages of XBB.1.16 (25.31%; n = 723), XBB.1.16.1 (10.85%; n = 310), XBB.2.3 (8.96%; n = 256), XBB.1.5 (6.89%; n = 197), XBB.1.9 (0.31%; n = 9), XBB.1 (5.28%; n = 151), XBB.2 (4.41%; n = 126), BQ.1.1 (1.68%; n = 48), BQ.1 (0.87%; n = 25), BA.2.75 (0.17%; n = 5), and BA.2 (1.01%; n = 29), as compared in Figure 2. Until April 10, 2023, XBB.1.16 sequences has been reported in 15 states and Union territories, with current relative growth advantage of 62% (56%–68%; 95% confidence interval [CI]) and contributes to 49% (46%–51%; 95% CI) of SARS‐CoV‐2 sequences over the previous 60 days. Researchers have posited that the XBB.1.16 variant depicts a new set of symptoms including high‐grade fever, cough, and itchy conjunctivitis. The XBB.1.16 strain precipitates mild respiratory symptoms and itchy, nonpurulent pediatric conjunctivitis or pink‐ eye with profound ocular discharge and sticky eyelids in 42.8% infant patients. Although, the variant affects the young infants more than older children, hospital admission was not required in either age group, and patients recovered with symptomatic treatment. Of the 276 patients infected with XBB.1.16 variant examined in Maharashtra, India, 92% had a symptomatic disease, with fever (67%), persistent cough (42%), rhinorrhea (33.7%), body ache (14.5%), and fatigue (14.1%). Of the total patients, 17.7% patients were comorbid and 91.7% had received their first dose of COVID‐19 vaccination. Home‐isolation was required for 74.3% cases, while 25.7% needed hospital admission (with mean stay duration of 6.6 ± 3.9 days) or institutional quarantine, of which 33.8% required oxygen therapy. While 2.5% (n = 7) patients died of the infection, most of them were elderly (aged 60 or more), had comorbidities and/or required supplemental oxygen therapy. Additionally, clinicians believe that the hybrid immunity obtained from active COVID‐19 infection as well as vaccinations and subsequent booster doses can neutralize the virus in vivo in humans, thereby reducing the number of casualties and hospital admissions. Moreover, such an immunity against the virus could be associated with the limited mutations that have been reported in the parts of the virus that are actively targeted by the human T‐cells, which leaves room for T‐cell mediated immune response following XBB.1.16 infections. The Indian Council of Medical Research (ICMR) has hypothesized that the higher number of COVID‐positive cases could result from increased testing rates in India, in the wake of the ongoing Influenza