Potential threat and possible global spread of the novel SARS-CoV-2 Omicron subvariants including XBB.1.16 during the Indian Premier League 2023: strict implementation of traveller guidelines suggested

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TL;DR

This letter warns that the 2023 Indian Premier League (IPL) could become a superspreader event for the highly transmissible SARS-CoV-2 Omicron subvariant XBB.1.16 (Arcturus), which has been detected in multiple Indian provinces and countries including the US, Australia, and the UK. The authors note that XBB.1.16 exhibits mutations in the spike (E180V, T478R) and non-spike regions that enhance immune evasion and infectivity, with a higher effective reproductive number than XBB.1 and XBB.1.5. They recommend strict implementation of traveller guidelines, genomic surveillance, COVID-appropriate behaviour (masking, hand hygiene, ventilation), and booster vaccination to mitigate risks during mass gatherings.

Full summary

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**Background:** This letter to the editor addresses the public health threat posed by emerging SARS-CoV-2 Omicron subvariants, particularly XBB.1.16 (Arcturus), in the context of the 2023 Indian Premier League (IPL)—a major global cricket event held from 31 March to 28 May 2023 in densely populated Indian metro cities. The authors highlight that XBB.1.16 is a recombinant descendant of the XBB variant, with two key spike substitutions (E180V in the N-terminal domain and T478R in the receptor-binding domain) that contribute to its infectivity. XBB.1.16 also carries ORF9b mutations in the non-spike region that may facilitate efficient immune evasion. The WHO has classified XBB.1.16 as a variant of interest (VOI). The letter notes that XBB.1.5 carries a rare F486P mutation in the RBD that enhances cell attachment and immune evasion, requiring two nucleotide substitutions in the same codon.

**Methods:** This is a narrative commentary/letter to the editor. The authors cite data from GISAID and INSACOG indicating that at least 344 XBB.1.16 sequences were identified in India, with Indian authorities submitting 49% of all XBB.1.16 sequences globally. They reference ECDC assessments and published reports on variant characteristics. No systematic literature search or quantitative synthesis was performed.

**Key Results:** The authors report that XBB.1.16 has a greater effective reproductive number compared to XBB.1 and XBB.1.5, leading to quicker transmission. A sharp rise in COVID-19 cases among children below 12 years has been noticed, though the authors caution it is too early to draw conclusions. Most reported cases have mild to moderate symptoms—high fever, severe headache, sore throat, cough, body pain, cold, abdominal discomfort, and itchy conjunctivitis—with no loss of smell or taste. Home isolation and treatment were sufficient for most cases. The authors note that India has poor booster dose coverage, and high-risk individuals (those with comorbidities including age, cardiac conditions, diabetes, chronic kidney disease, asthma, tuberculosis) need to be vigilant. The letter warns that mass gatherings like the IPL could become superspreader events, facilitating transmission of COVID-19 as well as other transmissible diseases (winter flu, hepatitis A and B, diarrhoea, measles) and multidrug-resistant bacteria.

**Clinical Implications:** The authors argue that currently available vaccines may be inefficient against emerging subvariants, though therapeutics appear to protect against severe symptoms, hospitalisation, and death. They recommend: (1) promotion of COVID-19 booster vaccination for enhanced protection; (2) development of new, more efficient vaccines and monoclonal antibodies; (3) strict implementation of traveller guidelines in a non-discriminatory manner; (4) targeted genomic surveillance of travellers; (5) basic COVID-appropriate measures (face-masking, hand-sanitising, social distancing); (6) testing and monitoring; and (7) surveillance of urban wastewater handling systems as an early warning tool. The letter emphasises that the unpredictable surge due to the COVID-19 'variant soup' of recently emerging subvariants is frightful and requires urgent public health action.